JP2006046496A - Axial flow type non-contact seal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact axial flow type non-contact seal to be used for a rotary joint having a small axial diameter. <P>SOLUTION: The axial flow type seal to be arranged around a rotating shaft comprises, at least, a seal ring and a secondary seal as an elastic body. The inner peripheral face of the seal ring has a fine clearance from the outer peripheral face of the rotating shaft. On at least one identical circumference of the inner peripheral face, a pressure groove is provided where a plurality of holes are arranged at equal spaces passing through the outer peripheral face into the inner peripheral face of the seal ring. Pressurized sealing gas is supplied from the outer peripheral face of the seal ring via the plurality of holes into the pressure groove to maintain the fine clearance between the inner peripheral face of the seal ring and the outer peripheral face of the rotating shaft so that the secondary seal holds the seal ring in the axial direction of the rotating shaft. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a shaft seal of a rotary shaft having a small shaft diameter. More particularly, the present invention relates to a compact axial flow type non-contact seal for use in a small shaft diameter rotary joint.

  As the shaft seal, a mechanical seal is usually attached to the shaft seal portion. However, in a shaft seal used for a rotary joint with a small shaft diameter, the size is small, so that cooling water cannot be secured and a mechanical seal cannot be applied. Therefore, in general, a lip seal is often applied. However, in the case of a lip seal, contamination such as abrasion powder of the lip is generated, and the lip has a short life, which causes a problem of maintenance load. Furthermore, since there is a dead end portion (cut), it is not suitable for application to the field of food / pharmaceutical manufacturing that requires sterilization. Labyrinth seals and the like are also used to avoid contamination due to wear of seal parts, but at present there is nothing perfect.

  As a non-contact seal with little possibility of contamination due to wear powder, etc., the internal pressure of the vertical rotating machine is lower than the external atmospheric pressure at the shaft through part of the fixed part of the vertical rotating machine, and the inside of the machine is sealed from the outside Therefore, a non-contact seal ring shaft seal device has been developed (Patent Document 1). A plan sectional view of this device is shown in FIG. The seal ring 2 disposed with a gap 8 around the rotary shaft 1 is provided with a plurality of radial introduction holes 3. The seal ring 2 is fixed to a storage box (not shown) by a pin 6 in an annular storage chamber 4, and a pressure sealing liquid 7 is supplied to the storage chamber 4 from the outside through a pressure sealing liquid supply hole 5. Is done. The supplied pressure sealing liquid 7 is supplied to the gap 8 through the introduction hole 3 of the seal ring 2. However, when the rotating shaft 1 rotates, the rotating shaft 1 fluctuates in the radial direction with respect to the gap 8 between the seal ring 2. In this apparatus, when the rotating shaft 1 rotates at a high speed, the seal ring 2 moves to the rotating shaft 1. It may become impossible to follow the fluctuation and contact may occur.

Therefore, a seal ring has been devised in which a circumferential groove is formed on the inner peripheral surface of the seal ring to prevent contact between the rotating shaft and the seal ring (Patent Document 2). A cross-sectional view of this device is shown in FIG. In FIG. 2, a seal ring 15 having a clearance from the rotating shaft 12 is disposed in the casing 11. In the casing 11, a shaft sealing liquid supply port 14 is formed on the high pressure chamber 13 side, and a shaft sealing liquid outlet 16 is formed on the low pressure chamber 17 side. A circumferential groove 20 is formed on the inner peripheral surface of the seal ring 15, and a plurality of drainage holes 21 communicating from the circumferential groove 20 to the low pressure chamber 17 are provided. Are provided with an introduction hole 18 communicating with the inner peripheral surface and a supply hole 19 with a smaller hole diameter. Therefore, the shaft seal liquid flowing from the supply port 14 flows through the gap between the rotating shaft 12 and the seal ring 15 to the low pressure chamber 17 side via the circumferential groove 20 and the drain hole 21. Alternatively, it flows to the low pressure chamber 17 side through the introduction hole 18 and the supply hole 19. However, this device is intended to be used for a relatively large-sized rotating shaft such as a gas compressor or a pump, and when applied to a rotating shaft having a small shaft diameter, the structure is complicated. There is a problem above. Furthermore, since a liquid is used as a fluid for shaft sealing, there is a risk of contamination of the shaft sealing liquid itself, which is not suitable for use in the manufacture of pharmaceuticals.
Japanese Patent Publication No.62-16354 Japanese Utility Model Publication No. 4-46146

  An object of the present invention is to provide a compact axial flow type non-contact seal for use in a shaft seal of a dispenser having a rotating shaft or a reciprocating shaft of a rotating device such as a rotary joint.

  The present invention includes at least a secondary seal composed of a seal ring and an elastic body, and the inner peripheral surface of the seal ring forms a minute gap with the outer peripheral surface of the rotating shaft, and at least one of the inner peripheral surfaces is the same On the circumference, there is provided a pressure groove in which a plurality of holes penetrating from the outer peripheral surface to the inner peripheral surface of the seal ring are arranged at equal intervals, and the pressurized seal gas is supplied from the outer peripheral surface of the seal ring. A minute gap between the inner peripheral surface of the seal ring and the outer peripheral surface of the rotating shaft is maintained by supplying the pressure groove through the plurality of holes, and the secondary seal is An axial flow type seal configured to sandwich the seal ring from an axial direction of the shaft is provided.

  In a preferred embodiment, the pressure grooves are continuous grooves or divided grooves on the same circumference.

  In another preferred embodiment, at least one continuous auxiliary groove is formed in parallel with the pressure groove on the inner peripheral surface of the seal ring.

  In still another embodiment, two or more pressure grooves are formed in parallel on the inner peripheral surface of the seal ring.

  In another preferred embodiment, two or more auxiliary grooves are provided across the pressure groove.

  In a preferred embodiment, the minute gap between the inner peripheral surface of the seal ring and the rotating shaft is between 10 μm and 500 μm.

  In another preferred embodiment, 0.2 mm to 2 mm orifices are respectively provided on the outer peripheral surface side of the plurality of holes.

  In a more preferred embodiment, the depth of the pressure groove or auxiliary groove is 5 μm to 2 mm.

  In a preferred embodiment, the seal ring material comprises a material selected from the group consisting of silicon carbide, tungsten carbide, titanium carbide, and silicon nitride.

  According to the present invention, since the seal gas is supplied to the groove on the inner peripheral surface through the hole provided in the seal ring, a minute gap between the seal ring and the shaft is maintained uniformly, and the shaft circumference is constant. A seal gas barrier having a pressure is formed. Since the seal ring of the present invention has such a relatively compact structure, it can be applied to a small-shaft rotary shaft or a shaft seal portion of a reciprocating shaft, which can conventionally only be attached with a lip seal. Since the seal ring of the present invention is non-contact, it does not wear, has a long life, and does not generate contamination. Furthermore, since it can be made into a structure which does not have a dead end part, propagation of bacteria can be prevented and it is applicable also when sterilization is required. In addition, since it can be completely sealed with a sealing gas, it can cope with the case of sealing powder.

  The axial flow type seal of the present invention is an axial flow type non-contact seal disposed around a rotating shaft, and includes a seal ring and a secondary seal. A first feature of the present invention is that at least one pressure groove is provided on the same circumferential surface of the inner circumferential surface of the seal ring, and preferably an auxiliary groove is further included. In the pressure groove, a plurality of holes penetrating from the outer peripheral surface to the inner peripheral surface are arranged at equal intervals. Then, the pressurized seal gas is supplied from the outer peripheral surface of the seal ring to the pressure groove provided on the inner peripheral surface through a plurality of holes, whereby the inner peripheral surface of the seal ring and the outer peripheral surface of the rotary shaft A minute gap between the two is maintained. The secondary seal is made of an elastic body, and sandwiches the seal ring from the axial direction of the rotating shaft.

  The pressure grooves may be continuous grooves on the same circumference, or may be divided grooves. When the pressure grooves are divided, the divided pressure grooves are arranged at equal intervals on the same circumference, and a seal gas for supplying pressurized seal gas to the inside of each pressure groove It is essential that the introduction holes are arranged at equal intervals (that is, the seal gas introduction holes are also arranged at equal intervals on the same circumference). The position of the seal gas introduction hole in the divided pressure groove is arbitrary, and may be determined in consideration of the characteristics of the equipment to be applied and the sealing conditions.

  In addition to the pressure groove, at least one auxiliary groove may be provided. This auxiliary groove is different from the pressure groove in that it does not have a hole penetrating from the outer peripheral surface to the inner peripheral surface. By providing this auxiliary groove, the axial flow of the supplied seal gas is introduced into the auxiliary groove, and dynamic pressure can be generated by the axial seal gas flow, and the auxiliary groove functions as a seal dam. Thus, the alignment effect and more stable shaft rotation are possible. The installation position (distance from the pressure groove) of the auxiliary groove is determined in consideration of the position of the pressure groove, the pressure of the sealing fluid, the pressure of the sealing gas, and the like. Considering the function of the auxiliary groove, it is usually preferable to provide it at the end of the inner peripheral surface of the seal ring.

  Further, a plurality of pressure grooves may be provided on the inner peripheral surface of the seal ring. By having a plurality of pressure grooves, a more stable alignment operation can be obtained. A plurality of pressure grooves and auxiliary grooves may be provided on the inner peripheral surface of the seal ring. By combining a plurality of pressure grooves and a plurality of auxiliary grooves, the above-mentioned effects can be exhibited synergistically and effectively function as an axial flow type non-contact seal even under difficult sealing conditions. The installation positions of the pressure groove and the auxiliary groove are determined in consideration of the pressure of the sealing fluid and the pressure of the sealing gas.

  The inner peripheral surface of the seal ring constituting the axial flow type seal of the present invention is preferably sized to form a minute gap of 10 μm to 500 μm with the outer peripheral surface of the rotating shaft.

  Further, the depth of the pressure groove and the auxiliary groove provided in the seal ring is preferably 5 μm to 2 mm from the viewpoint of maintaining the pressure of the seal gas, and 30 μm to 2 mm which can eliminate the disturbance of the fluid film of the seal gas. More preferably.

  An orifice is provided on the outer peripheral surface side of the seal gas introduction hole as necessary. The orifice has a function of making the flow rate of the supplied sealing gas constant. In the present invention, the size of the orifice is preferably 0.2 mm to 2 mm.

  Examples of the material for the seal ring include carbon, silicon carbide, tungsten carbide, titanium carbide, silicon nitride, aluminum oxide, and stainless steel. A material having a relatively small mass such as carbon, silicon carbide, tungsten carbide, titanium carbide, and silicon nitride is preferably used in that it is excellent in following the axial fluctuation.

  Examples of the secondary seal 130 made of an elastic body include an O-ring and a rubber sheet. By using an elastic body as the secondary seal, it becomes easy to follow the shaft fluctuation of the rotating shaft.

  Hereinafter, the various embodiments of the axial flow type seal of the present invention will be described, but the structure of the inner peripheral surface of the seal ring will be mainly described, and the above description can be used for the other structural portions. The description is omitted.

  The axial flow type seal of the present invention comprises at least a seal ring and a secondary seal. 3A and 3B show a first embodiment of the axial flow type seal according to the present invention. FIG. 3A is a longitudinal side view showing the entire configuration, and FIG. 3B is an AA view of the seal ring in FIG. 'Cross sectional views and (c) and (d) are developed views of the inner diameter of the seal ring.

  In FIG. 3, an axial flow type seal 100 of the present invention includes a seal ring 120 attached to a rotary shaft 500, a secondary seal 130 made of an elastic body that sandwiches the seal ring 120 from the rotary shaft direction, and a casing that covers the seal ring 120. 110, a seal gas supply port 112 for supplying a seal gas to the space X in the casing 110. The inner peripheral surface of the seal ring 120 forms a minute gap Y with the outer peripheral surface of the rotating shaft 500. As shown in FIG. 3B, a plurality of holes (seal gas) penetrating from the outer peripheral surface to the inner peripheral surface of the seal ring 100 are formed on at least one same circumference of the inner peripheral surface of the seal ring 100. Pressure grooves 126a in which introduction holes) 122 are arranged at equal intervals are provided.

  The axial flow type seal 100 of the present invention is characterized by having a pressure groove 126 a on the inner peripheral surface of the seal ring 120. The pressurized seal gas is supplied from the seal gas supply port 112 to the space X outside the seal ring 120 serving as a rectifying unit, and the pressure of the seal gas is made uniform. Enter 122. The seal gas is supplied to a gap Y formed by the seal ring 120 and the rotary shaft 500 via a pressure groove 126 a provided on the inner peripheral side of the introduction hole 122. The seal gas supplied to the gap Y flows from the pressure groove 126a to the inside of the machine, and it becomes possible to form a rigid seal gas layer on the same circumference in the circumferential direction of the rotary shaft 500. An effect (alignment effect) of keeping the shaft outer peripheral surface parallel to the inner peripheral surface of the seal ring can be exhibited. Therefore, the seal ring 120 and the rotating shaft 500 do not contact each other. For this reason, there is no wear of the seal ring or shaft, and no contamination occurs. Furthermore, since it can be made into a structure which does not have a dead end part, propagation of bacteria can be prevented and it is applicable also when sterilization is required. Further, since the secondary seal composed of an elastic body is used to sandwich the seal from the direction of the rotation axis, there is an effect of confining the seal gas inside the machine in the machine without affecting the alignment function. Therefore, it is possible to cope with sealing powder.

  The pressure groove 126a may be a continuous groove or a divided groove. FIGS. 3C and 3D are illustrations of divided grooves, and are examples in which the seal gas introduction holes 122 are provided at different positions. When the pressure grooves 126a are divided, the pressure grooves 126 are arranged at equal intervals on the same circumference, and a seal gas for supplying pressurized seal gas to the inside of each pressure groove 126a. It is essential that the introduction holes 122 are arranged at equal intervals (that is, the seal gas introduction holes 122 are also arranged at equal intervals on the same circumference). The position of the sealing gas introduction hole 122 in the divided pressure groove 126a is arbitrary as shown in FIGS. 3C and 3D, and is determined in consideration of the characteristics of the equipment to be applied and the sealing conditions. do it.

  When the pressure groove 126a is divided, in addition to the static pressure effect of the seal gas supplied from the seal gas introduction hole 122, the pressure groove 126a is moved by the interaction between the circumferential seal gas flow generated by the rotation of the shaft and the divided grooves. Since pressure is generated, stability during high-speed rotation can be increased.

  By having the pressure groove 126a, the alignment function is effectively exhibited. In order to more effectively demonstrate this alignment function, a continuous auxiliary groove ( The auxiliary groove preferably does not have the seal gas introduction hole 122), and is preferably formed in parallel with the pressure groove 126a. In order to achieve a more stable alignment effect, it is preferable to provide a plurality of pressure grooves. Furthermore, it is good also as a structure provided with the some pressure groove and the auxiliary groove. Hereinafter, these examples will be described.

  A second embodiment of the axial flow type seal of the present invention will be described. The second aspect is an aspect having at least one auxiliary groove in addition to the pressure groove. An example is shown in FIG. 4A is a longitudinal side view of the entire apparatus, and FIG. 4B is a developed view of the inner diameter of the seal ring 220. In this embodiment, an O-ring is used as the secondary seal 230. The inner circumferential surface of the seal ring 220 is provided with a pressure groove 226a divided on the circumference of the inner circumferential surface, and a seal gas introduction hole 222 is opened in each pressure groove 226a. One continuous auxiliary groove 226b is provided in parallel to the pressure groove 226a.

  In this second embodiment, the pressurized seal gas is supplied from the seal gas supply port 212 to the space X outside the seal ring 220 serving as a rectifying unit, and the pressure of the seal gas is made uniform. The plurality of seal gas introduction holes 222 are entered through the. The seal gas is supplied to the clearance Y with the rotary shaft through the divided pressure groove 226a provided on the inner peripheral side of the introduction hole 222. Since the auxiliary groove 226b that is continuous on the same circumference is provided in parallel with the pressure groove 226b, the axial flow of the supplied seal gas is introduced into the auxiliary groove 226b. Therefore, the dynamic pressure due to the axial seal gas flow can be generated, and the auxiliary groove 226b functions as a seal dam for blocking the seal gas flowing in the axial direction. As a result, the rigidity of the fluid film formed by the gas existing on the inner peripheral surface of the seal ring 220 can be increased, and the alignment effect by the improvement of the load capacity and the more stable rotation of the shaft can be achieved. As a result, as in Example 1, the effects of preventing wear of the seal, preventing the occurrence of contamination, preventing the growth of bacteria, and enabling the powder to be sealed are also brought about.

  FIG. 5 shows an example in which two auxiliary grooves are provided in the second embodiment. FIG. 5A is a longitudinal side view showing the entire configuration, and FIG. 5B is a developed view of the inner diameter of the seal ring in FIG. 5 (a) and 5 (b), a rubber sheet is used as a secondary seal, and the pressure groove 326a has a continuous shape. Two auxiliary grooves 326b are arranged on both sides of the pressure groove 326a in parallel with the pressure groove 326a. Is provided. FIGS. 5C and 5D are the same as FIGS. 5A and 5B except that an O-ring is used as a secondary seal and the pressure groove 326a is divided.

  5A and 5B, the axial flow type non-contact seal 300 is disposed around the rotation shaft 500 and includes a seal ring 320 and a secondary seal (rubber sheet) 330 in the casing 310. The inner circumferential surface of the seal ring 320 is provided with a pressure groove 326a continuous on one circumference, and two auxiliary grooves 326b are disposed in parallel to the pressure groove 326a so as to sandwich the pressure groove 326a (that is, the same circle). To be continuous on the circumference).

  In the axial flow type non-contact seal 300, the pressurized seal gas is supplied to the space X outside the seal ring from a seal gas supply port 312 provided in the casing 310, and further, a plurality of seals are supplied via the orifice 324. Enter the gas introduction hole 322. The seal gas is supplied to the clearance Y with the rotary shaft through a continuous pressure groove 326a provided on the inner peripheral side of the introduction hole 322. The axial flow of the supplied seal gas is introduced into the two auxiliary grooves 326b. Therefore, dynamic pressure can be generated by the axial seal gas flow, and the two auxiliary grooves 326b function as seal dams for blocking the seal gas flowing in the axial direction. For this reason, the rigidity of the fluid film formed by the gas existing on the inner peripheral surface of the seal ring 320 can be further increased as compared with the case where there is one auxiliary groove 326b, and the alignment effect by the improvement of the load capacity and further Stable shaft rotation is possible. As a result, as described above, the effects of preventing the wear of the seal, preventing the occurrence of contamination, preventing the growth of bacteria, and enabling the sealing of the powder are also brought about.

  5 (c) and 5 (d) differ from FIGS. 5 (a) and 5 (b) in that the pressure groove 326a is divided. As described above, when the pressure groove 326a is divided, the stability during high-speed rotation can be increased.

  In the second embodiment, the distance between the pressure groove 326a and the auxiliary groove 326b (the distance between the pressure groove 226a and the auxiliary groove 226b in FIG. 4) is the pressure of the sealing fluid and the sealing gas as described above. However, in consideration of the function of the auxiliary groove, it is usually preferable to provide it at the end of the inner peripheral surface of the seal ring. In the case shown in FIG. 5, the pressure groove 326a may be provided at the center of the seal ring 320, and the auxiliary groove 326b may be provided at the end of the seal ring 320 symmetrically with the pressure groove 326a and at equal intervals.

  A third embodiment of the axial flow type seal of the present invention will be described. This third aspect is an aspect having two or more pressure grooves. An example is shown in FIG. In FIG. 6A, two pressure grooves 426 a having seal gas introduction holes 422 are provided in parallel on the inner peripheral surface of the seal ring 420. By having the plurality of pressure grooves 426a, the distribution of the seal gas on the inner peripheral surface (gap Y) of the seal ring 420 can be made uniform, and an alignment effect excellent in stability can be achieved.

  FIG. 6B shows an embodiment in which two pressure grooves 426a are provided in parallel as in FIG. 6A. This position is determined in consideration of the pressure of the sealing fluid and the pressure of the sealing gas.

  FIG. 6C shows a case where two pressure grooves 426 a and one auxiliary groove 426 b are provided on the inner peripheral surface of the seal ring 420. There may be a plurality of auxiliary grooves 426b. Thus, by combining a plurality of pressure grooves and a plurality of auxiliary grooves, and further combining the structure of the pressure grooves (continuous or divided), the above-mentioned effects can be exhibited synergistically, which is difficult. Even under sealing conditions, it functions effectively as an axial flow type non-contact seal. When a plurality of pressure grooves and a plurality of auxiliary grooves are arranged, the alignment operation and the rotational stability of the shaft are enhanced. To further enhance this effect, a plurality of auxiliary grooves are parallel to the pressure grooves with the pressure grooves interposed therebetween. It is preferable to be formed. The position of the auxiliary groove is determined in consideration of the position of the pressure groove, the pressure of the sealing fluid and the pressure of the sealing gas (that is, the distance to the pressure groove is determined), but under normal sealing conditions, Even when the distance between the pressure groove and the adjacent auxiliary groove is equal, a sufficient alignment effect and stable sealing performance are expected. FIG. 6D shows a case where there are two pressure grooves and two auxiliary grooves. The seal ring 420 in FIG. 6D is an example in which the distance a between the pressure groove 426a and the auxiliary groove 426b is equal. Such a seal ring is expected to have stable sealing performance and alignment effect under normal sealing conditions.

  Since the axial flow type non-contact seal of the present invention has a relatively compact structure, it can be applied to a shaft seal portion of a rotary shaft having a small shaft diameter, to which only a lip seal can be conventionally attached. The seal ring of the present invention has no wear due to non-contact, and therefore has a long life and does not generate contamination. Furthermore, since it can be set as a structure which does not have a dead end part, the proliferation of bacteria can be prevented and it is applicable also when sterilization is required. Further, since it can be completely sealed with a sealing gas, it can also be used for powder. Thus, it is suitable for an apparatus used in the field of manufacturing foods and pharmaceuticals that are relatively small and need to be sterilized.

It is a plane sectional view of the conventional non-contact seal ring shaft sealing device (patent documents 1). It is a plane sectional view of the conventional non-contact seal ring shaft sealing device (patent documents 2). It is a figure which shows the 1st embodiment of this invention. It is a figure which shows the 2nd embodiment of this invention. It is a figure which shows another example of the 2nd embodiment of this invention. It is a figure which shows the 3rd embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotating shaft 2 Seal ring 3 Introduction hole 4 Storage chamber 5 Pressure sealing liquid supply hole 6 Pin 7 Pressure sealing liquid 8 Crevice 11 Casing 12 Rotating shaft 13 High pressure chamber 14 Shaft sealing liquid supply port 15 Seal ring 16 Flow of shaft sealing liquid Outlet 17 Low pressure chamber 18 Inlet hole 19 Supply hole 20 Circumferential groove 21 Drain hole 100, 300, 400 Axial flow type seal 110, 310 Casing 112, 212, 312 Seal gas supply port 120, 220, 320, 420 Seal ring 122 222, 322, 422 Seal gas introduction holes 124, 224, 324, 424 Orifices 126a, 226a, 326a, 426a Pressure grooves 126b, 226b, 326b, 426b Continuous grooves 130, 230, 330, 430 Secondary seal 500 Rotating shaft X Outer space Y gap

Claims (5)

  An axial flow type seal disposed around a rotating shaft, comprising at least a secondary seal made of a seal ring and an elastic body, and the inner peripheral surface of the seal ring has a minute gap from the outer peripheral surface of the rotating shaft. A pressure groove is formed on the same circumference of at least one of the inner peripheral surfaces, and a plurality of holes are provided at equal intervals from the outer peripheral surface to the inner peripheral surface of the seal ring. By supplying the sealed gas from the outer peripheral surface of the seal ring to the pressure groove through the plurality of holes, a small gap is formed between the inner peripheral surface of the seal ring and the outer peripheral surface of the rotary shaft. An axial flow type seal configured to maintain and the secondary seal sandwiches the seal ring from the axial direction of the rotating shaft.   The axial flow type seal according to claim 1, wherein the pressure groove is a continuous groove or a divided groove on the same circumference.   The axial flow type seal according to claim 1 or 2, wherein at least one continuous auxiliary groove is formed in parallel with the pressure groove on an inner peripheral surface of the seal ring.   The axial flow type seal according to any one of claims 1 to 3, wherein two or more pressure grooves are formed in parallel on an inner peripheral surface of the seal ring.   The axial flow type seal according to any one of claims 1 to 4, wherein two or more auxiliary grooves are provided with the pressure groove interposed therebetween.

Images