JP3079562B2 - Two-way non-contact mechanical seal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an improvement of a non-contact mechanical seal,
More specifically, the present invention relates to a non-contact mechanical seal used as a shaft sealing device for a fluid device such as a gas turbine or a compressor under a high peripheral speed condition.

[Conventional technology]

2. Description of the Related Art Conventionally, a non-contact mechanical seal for sealing between a rotating shaft and a housing in a compressor or the like has already been provided. For example, Japanese Patent Publication No. 1-2509 discloses that any one of sealing surfaces facing a rotating ring hermetically fixed to a rotating shaft and a non-rotating ring hermetically mounted on a housing and urged in the axial direction by pressing means. A non-contact mechanical seal in which a number of spiral grooves having the same length and having an advance angle with respect to the relative rotation direction are provided on one seal surface at regular intervals in a circumferential direction, and a sealed fluid is pumped between the seal surfaces. Is provided.

However, the conventional non-contact mechanical seal has the above-described sealing performance only when the rotating ring rotates in a specific forward direction with respect to the non-rotating ring. The gas is discharged, the pressure is reduced, and a vacuum is established, so that the two sealing surfaces come into firm contact.

In operation of an actual compensator or the like, the rotating ring normally rotates in a set forward direction, but often reversely rotates at the beginning of rotation or immediately before stopping. In such a case, the two sealing surfaces come into contact with each other in a strong contact state, so that the abrasion of the sealing surfaces is increased and frictional heat is generated, which may impair the characteristics of the surfaces.

On the other hand, even in the case of rotating only in the forward direction, in order to seal both ends of the rotating shaft penetrating the housing, the arrangement of the rotating ring and the non-rotating ring in the axial direction of the rotating shaft is reversed, The spiral groove formed on the sealing surface must also be formed to have an advancing angle in the opposite direction. This means that two types of symmetric non-contact mechanical seals are required, which leads to an increase in cost.

[Problems to be solved by the invention]

In view of the above situation, the present invention seeks to solve the problem that a spiral groove formed on a sealing surface is formed regardless of whether the rotating direction of a rotating ring with respect to a non-rotating ring is forward or reverse. The present invention provides a two-way non-contact mechanical seal capable of sealing in a non-contact state by pumping a sealed fluid between seal surfaces.

[Means for solving the problem]

According to the present invention, in order to solve the above-mentioned problem, a rotating ring hermetically fixed to a rotating shaft and a non-rotating ring axially urged and sealed to a housing and axially urged by pressing means are brought into contact with each other. Helical grooves which extend from the outer peripheral edge or the inner peripheral edge as base ends and are closed at their ends are provided in a substantially mirror image relationship with each other, and the spiral grooves of one of the sealing surfaces are rotated with the rotation shaft in the forward direction. To generate dynamic pressure,
A two-way non-contact mechanical seal in which a dynamic pressure is generated in a spiral groove on the other seal surface with the reverse rotation is configured.

Further, the dam width ratio of the spiral groove was set to about 0.2 to 0.8.

Then, in order to seal between the housing and the rotating shaft which normally rotates only in a predetermined forward direction, the number of spiral grooves having an advancing angle with respect to the relative rotation direction due to the forward rotation of the rotating shaft is set to the other. Either more were set or its width was set wider than the other, or its depth was set deeper than the other.

Further, in order to seal between the housing and the rotating shaft which rotates in either the forward direction or the reverse direction, the spiral grooves formed on both the sealing surfaces have a perfect mirror image relationship.

[Action]

The two-way non-contact mechanical seal of the present invention having the above contents extends to the sealing surface of the rotating shaft and the sealing surface of the non-rotating ring, with the outer peripheral edge or the inner peripheral edge as a base end,
By providing spiral grooves having substantially mirror image relationships with each other with their ends closed, the sealed fluid is pressure-fed between the seal surfaces by the fluid transport action of the spiral grooves formed on one seal surface with forward rotation, and The sealed fluid is similarly pumped between the sealing surfaces by the fluid transport action of the spiral groove formed on the other sealing surface with the reverse rotation, and even if the rotating shaft rotates in the forward direction or the reverse direction, both sealing surfaces are not rotated. It seals in a contact state.

Further, the number of spiral grooves having an advance angle with respect to the relative rotation direction due to the forward rotation of the rotating shaft is set to be larger than the other, or the width thereof is set wider than the other, or the depth is set deeper than the other. By setting, the sealing performance is improved when the rotating shaft is rotating in the forward direction, and if the rotating shaft is stopped in the reverse direction when it stops, the sealing surfaces are not so tight that the two sealing surfaces do not contact tightly. Maintain the contact state.

When the spiral grooves formed on both sealing surfaces have a perfect mirror image relationship, substantially the same non-contact sealing is performed regardless of whether the rotation direction of the rotating shaft is the forward direction or the reverse direction. It has performance.

〔Example〕

Next, the present invention will be described in further detail with reference to embodiments shown in the accompanying drawings.

FIG. 1 shows the entire structure of a two-way non-contact mechanical seal M according to the present invention, and includes a housing 1 and the housing 1.
And the rotating shaft 2 penetrating through the open end. Here, in the figure, A is the atmospheric pressure (low pressure) side, and B is the high pressure (seal pressure).
Side view.

The two-way non-contact mechanical seal M of this embodiment includes a rotating ring 3 hermetically fixed to the rotating shaft 2 and a non-rotating ring 4 hermetically mounted on the housing 1. The sealing surfaces 5 and 6 are brought into contact with each other, and the non-rotating ring 4 is made axially movable in a sealed state, and the sealing surfaces 5 and 6 are approached by pressing means 7 associated with the housing 1. It is energizing. As shown in FIG. 2, a spiral groove 8 extending inward from the outer peripheral edge and having an advancing angle with respect to the relative rotation direction is provided on the sealing surface 5 of the rotating ring 3 at a constant interval in the circumferential direction. Many are provided for each. On the other hand, as shown in FIG. 3, the sealing surface 6 of the non-rotating ring 4 is provided with a spiral groove 9 extending inward from the outer peripheral edge thereof and having a receding angle with respect to the relative rotation direction. Many are provided for each interval. That is, the screw groove 8
And the spiral groove 9 are formed so as to have a substantially mirror image relationship with each other when the two sealing surfaces 5 and 6 are in contact with each other. here,
The inner ends of the thread grooves 8 and 9 are closed, ie
And 6 are flush with the other parts.

The rotating ring 3 is coaxially extrapolated to a fixed sleeve 10 coaxially extrapolated to the rotating shaft 2, and
The side opposite to the sealing surface 5 is abutted against a flange 11 extending from one end of the flange 10, and the flange 11 is fitted over the fixed sleeve 10 in a state of being abutted against a step 12 formed on the rotating shaft 2. The end of the fastening sleeve 13 and the end of the fixed sleeve 10 is
By tightening with a holding nut 14 screwed to the shaft, it is fixed to the rotating shaft 2 together with the fixed sleeve 10, and between the rotating shaft 2 and the flange portion 11, between the rotating ring 3 and the fixed sleeve 10, and between the rotating ring 3 and the flange portion 11. O ring 15,1 each
6, 17 are interposed and sealed.

The non-rotating ring 4 is axially movable at a predetermined position by an annular holding device 18 hermetically sealed and fixed to the housing 1 to be sealed and held, and a pressing means 7 seals the sealing surface 5 of the rotating ring 3 The seal surface 6 of the non-rotating ring 4 is urged in the approaching direction. Here, the holding device 18 has one end on the outer periphery abutting on the step portion 19 of the housing 1 and the other end on the fixed sleeve 20 to regulate the movement in the axial direction. An O-ring 21 is interposed between the outer circumferences of the non-rotating ring 4 and an O-ring 23 is interposed between the outer circumference of an annular sliding portion 22 extending in the axial direction from the inner peripheral edge and the inner circumference of the non-rotating ring 4. The rotary ring 4 is axially movable in a sealed state. Then, the other end of the pressing means 7 made of an elastic member such as a plurality of coil springs having one end engaged with the holding device 18 is connected to the end opposite to the sealing surface 6 of the non-rotating ring 4 via an annular disk 24. The non-rotating ring 4 is elastically urged in the direction of the rotating ring 3 so that a pressing force always acts in a direction in which the sealing surfaces 5 and 6 approach each other.

The non-rotating ring 4 does not completely contact the rotating ring 3 during rotation, but the rotating shaft 2 starts rotating from a stationary state and slides with the rotating ring 3 due to contact resistance at an initial stage. On the other hand, when the rotation speed of the rotating shaft 2 is equal to or higher than a predetermined value, the dynamic pressure increases and the sealing surfaces 5 and 6 slide, so that the non-rotating ring 4 substantially stops sliding. Note that the rotational speed at which the sliding stops substantially differs depending on the viscosity of the fluid interposed between the sealing surfaces 5 and 6.

In the present embodiment, the rotating ring 3 and the non-rotating ring 4
Although the example of the non-contact mechanical seal M provided with a pair has been shown, a tandem type seal in which a plurality of these are arranged in relation to each other in the axial direction can also be adopted.

FIGS. 2 and 3 show spiral grooves 8 and 9 formed in the sealing surfaces 5 and 6 of the rotating ring 3 and the non-rotating ring 4 of the present invention.
Each of the patterns shown in FIG. 1 is shown, and the two spiral grooves 8, 9 are formed in a perfect mirror image relationship.

 Next, the dam width ratio is defined by the following equation.

Here, OD is the outer shape of the common part of the sealing surfaces 5 and 6, ID is the inner diameter, and GD is the diameter of the contour circle formed at the boundary between the groove region of the spiral groove and the flat region.

Formula (1) is a formula applied when the spiral groove is formed with the outer peripheral side of the sealing surface as a base end, and formula (2) is a formula applied when the inner circumferential side is formed with a base end as a base end. In the present invention, the dam width ratio of the spiral grooves 8, 9 is set to about 0.2 to 0.8. The optimum value of the dam width ratio varies depending on other parameters, for example, the type and pressure of the sealed fluid, the number of revolutions, and the like. As a more preferable value, the dam width ratio of the short spiral groove 8 is about
0.3 to 0.6. The dam width ratio between the rotating ring 3 and the non-rotating ring 4 can be changed.

Here, the spiral groove in the present invention has a depth of about 2 to 15 μm, and the width and the angle of the advancing angle are determined by the sealing pressure and the number of rotations of the sealed fluid. In this embodiment, a spiral groove 8 having an advancing angle is formed on the sealing surface 5 of the rotating ring 3, and a spiral groove 9 having a receding angle is formed on the sealing surface 6 of the non-rotating ring 4. The opposite relationship can be formed.

Further, the pattern of the spiral groove is not limited to those shown in FIGS. 2 and 3, and various patterns can be adopted. Although not shown, the number of the spiral grooves 8 or 9 having an advancing angle with respect to the relative rotation direction is set to be larger than that of the other in the forward rotation which is the normal rotation direction of the rotation shaft 2, or the width thereof is increased. By setting it wider than the other or setting the depth deeper than the other, the flow rate to be pumped between the sealing surfaces 5 and 6 is reversed by the spiral groove 9 or 8 having a receding angle with respect to the relative rotation direction. The flow rate discharged to the high pressure side B is set to be small, and the pressure of the sealing surfaces 5 and 6 is set to be sufficiently higher than the sealing pressure of the sealed fluid. Even when the spiral grooves 8 and 9 are formed in a perfect mirror image relationship, as in the present embodiment, the groove width at the inner end is narrower than the groove width at the open end in the planar shape of the spiral groove. It is experimentally that the flow discharged to the high-pressure side B by the spiral groove having the receding angle is smaller than the flow flowing by pressure between the sealing surfaces 5 and 6 by the spiral groove having the advance angle with respect to the relative rotation direction. Has been verified.

Then, the method of forming the spiral groove on the surface of the sealing surface is as follows: the rotating ring 3 is formed into a predetermined shape using a material such as tungsten carbide, silicon carbide, silicon nitride, alumina ceramic, or a metal material.
After the non-rotating ring 4 is formed, a spiral groove is formed on a surface serving as a sealing surface by using a chemical, physical, or electrochemical method. For example, it can be formed by etching, blasting of powder, and various plating processes.

Next, in the two-way non-contact mechanical seal M of the present embodiment, the non-rotating ring 4 receives a pressure on the inner periphery thereof. The value is set to 0.5 to 1.5.

Thus, a spiral groove 8 having an advancing angle is formed on the sealing surface 5 of the rotating ring 3 with respect to a specific forward rotation direction of the rotating shaft 2, and the receding angle is formed on the sealing surface 6 of the non-rotating ring 4. The concrete operation of the case where the spiral groove 9 having the above-described shape and the two spiral grooves 8, 9 are formed in a perfect mirror image relationship will be described below.

First, as shown in FIG. 4, when the rotating shaft 2 rotates at a high speed in the forward direction, a sealing fluid having a predetermined sealing pressure is applied between the sealing surfaces 5 and 6 by a spiral groove 8 formed in the sealing surface 5. As a result, as shown in FIG. 5, a dynamic pressure P _O1 higher than the seal pressure is generated inside the seal surface in the radial direction (near the end of the spiral groove 8), while the seal of the non-rotating ring 4 is formed. Since the spiral groove 9 formed on the surface 6 has a receding angle with respect to the relative rotation direction of the non-rotating ring 4, the fluid existing between the sealing surfaces 5, 6 by the spiral groove 9 at the radial outer periphery. discharged to a certain high pressure side B, reducing the pressure between the sealing surfaces 5 and 6, as a result, the but dynamic pressure P _O1 is changed to P _O as shown, the peak value of the dynamic pressure P _O is Since the pressure is sufficiently higher than the sealing pressure, it is possible to seal the sealed fluid.

Next, as shown in FIG. 6, when the rotating shaft 2 rotates at a high speed in the reverse direction, the spiral groove 9 formed in the sealing surface 6 of the non-rotating ring 4 is moved in the relative rotation direction of the non-rotating ring 4. Since it has an advancing angle with respect to this, the sealed fluid having a predetermined sealing pressure is pumped between the sealing surfaces 5 and 6 by the spiral groove 9,
As a result, as shown in FIG. 7, a dynamic pressure P _I1 higher than the seal pressure is generated inside the seal surface in the radial direction (near the end of the spiral groove 9), while being formed on the seal surface 5 of the rotating ring 3. Since the formed spiral groove 8 has a receding angle with respect to the rotation direction of the rotating ring 3, the sealing surfaces 5, 6 are formed by the spiral groove 8.
The fluid existing therebetween is discharged to the high-pressure side B, which is the outer circumference in the radial direction, and the pressure between the sealing surfaces 5 and 6 is reduced. As a result, the dynamic pressure P _I1 is changed to P _I as shown in FIG. , This dynamic pressure P
_Since the peak value of _I is sufficiently higher than the sealing pressure, it is possible to seal the sealed fluid.

In this embodiment, the dynamic pressure P _O for forward rotation is slightly higher than the dynamic pressure P _I for reverse rotation. This is because the relative rotational speed of the rotating ring 3 with respect to the stationary sealed fluid is substantially close to its rotational speed, while the relative rotating speed of the non-rotating ring 4 with respect to the sealed fluid is extremely small compared to that. Pressure feeding between the sealing surfaces 5 and 6 by the spiral groove 8 having an advancing angle with respect to the forward rotation of the rotating shaft 2
A spiral groove 9 having an advance angle with respect to the reverse rotation of the rotating shaft 2
This is because it is superior to the pressure feeding between the sealing surfaces 5 and 6 due to the pressure.

Thus, the non-rotating ring 4 moves in the axial direction against the pressing force of the pressing means 7 due to the dynamic pressure, and the dynamic pressure by the fluid and the pressing force of the pressing means 7 are balanced, that is, the seal A non-contact state having a parallel gap between the surfaces 5 and 6 results. In this state, the sealed fluid inevitably flows between the rotating shaft 2 and the non-rotating ring 4 from between the sealing surfaces 5 and 6, and slightly leaks to the atmosphere side.

The operation described above is the case of the operation in which the rotation speed of the rotating shaft 2 has reached a sufficiently high rotation speed in the forward rotation or the reverse rotation, but the dynamic pressure immediately before the start or immediately before the stop is low. Even when it is low, the flat portions of the sealing surfaces 5 and 6 are in close contact with each other, so that the leakage amount of the sealed fluid is small. Further, when the two-way non-contact mechanical seal M of the present invention is incorporated in a device that rotates only in the forward direction and is used, even if abnormal reverse rotation occurs at the beginning of the start or immediately before the stop, the seal surfaces of the two seals can be used.
Since the sealed fluid is pumped between 5, 6, the sealing surfaces 5, 6 are not firmly fixed in any case, and the sealing surfaces 5, 6 are not worn or deteriorated by frictional heat. is there.

Further, in the case where the device for mounting the two-way non-contact mechanical seal M of the present invention is one in which the rotation direction of the rotating shaft 2 is only the forward rotation during the operation in principle, it is necessary to improve the sealing performance. It is desirable that the dynamic pressure by the spiral groove having an advance angle with respect to the relative rotation direction is as high as possible. In that case, the number of the spiral grooves 8 or 9 having an advancing angle with respect to the normal rotation direction is set more than the other, the width is set wider than the other, or the depth is set deeper than the other. If so, it is possible to provide excellent sealing performance during forward rotation.

On the other hand, as in the case where the rotating shaft 2 is disposed in a penetrating state with respect to the housing 1 and the two-way non-contact mechanical seals M, M of the present invention are attached to both ends of the rotating shaft 2 so as to face each other, the sealing in a specific rotating direction is performed. In some cases, it is desired to substantially match the performance with the sealing performance against rotation in the opposite direction. For this purpose, it is conceivable to form the spiral grooves 8 and 9 so as to have a perfect mirror image relationship with each other. The same sealing performance may not be obtained for the rotation of
As described above. In that case, by adjusting the planar shape of the spiral groove or by adjusting the number of grooves, groove width, groove depth, groove length, etc. as described above, if there is a slight change from a perfect mirror image relationship, It is possible in principle.

〔The invention's effect〕

According to the above-described two-way non-contact mechanical seal of the present invention, the non-rotational ring which is axially movable and hermetically mounted on the rotating ring and the housing which is sealed and fixed to the rotating shaft, and is urged in the axial direction by the pressing means. In a non-contact mechanical seal in which a spiral groove is provided on a seal surface that is in contact with a ring and a sealed fluid is pressure-fed between the seal surfaces, an outer peripheral edge or an inner peripheral edge is provided on both seal surfaces of the rotating ring and the non-rotating ring. Extending as a base end, and having screw grooves that are substantially mirror-image relative to each other and whose ends are closed, advancing angle with respect to the relative rotation direction formed on one seal surface with the forward rotation of the rotating shaft. The sealed fluid can be pumped between the sealing surfaces by the fluid transport action of the spiral groove having the sealing surface, and the pressure between the sealing surfaces can be made sufficiently higher than the sealing pressure of the sealed fluid for sealing. In addition, the sealed fluid is similarly pressure-fed between the sealing surfaces by the fluid transport action of the spiral groove having an advancing angle with respect to the relative rotation direction formed on the other sealing surface with the rotation of the rotating shaft in the opposite direction, and sealing. Thus, even when the rotating shaft rotates in the forward or reverse direction, both sealing surfaces can be sealed in a non-contact state.

Therefore, even if reverse rotation occurs immediately before or immediately after the rotation of the rotating shaft, as in the case of a conventional non-contact mechanical seal, wear between the sealing surfaces due to strong contact between the sealing surfaces increases, and frictional heat increases. Thus, there is no problem that the surface characteristics are deteriorated and the characteristics of the surface are impaired.

Also, in order to seal both ends of the rotating shaft penetrating the housing, the arrangement of the rotating ring and the non-rotating ring in the axial direction of the rotating shaft is reversed. However, according to the present invention, even if the same two-way non-contact mechanical seal is attached to both ends of the rotating shaft in opposition to each other, one of the screw grooves has a relative rotational direction. , Both have good sealing performance, and cost can be reduced.

Further, the number of spiral grooves having an advance angle with respect to the relative rotation direction due to the forward rotation of the rotating shaft is set to be larger than the other, or the width thereof is set wider than the other, or the depth is set deeper than the other. By setting, the sealing performance can be improved when the rotating shaft rotates only in the forward direction during normal operation, and even when the rotating shaft rotates in the reverse direction, the two sealing surfaces are in firm contact. The non-contact state can be maintained to the extent that it does not occur.

When the spiral grooves formed on both sealing surfaces have a perfect mirror image relationship, substantially the same non-contact sealing is performed regardless of whether the rotation direction of the rotating shaft is the forward direction or the reverse direction. It can be set to have high performance, and the machining of the spiral groove is facilitated, so that the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a principal part in a state where a two-way non-contact mechanical seal of the present invention is mounted between a rotating shaft and a housing. FIG. 2 shows an example of a pattern of a spiral groove formed on a sealing surface of a rotating ring. FIG. 3 is an end view showing an example of a spiral groove pattern formed on the sealing surface of the non-rotating ring, and FIG. 4 is a simplified diagram showing the positional relationship between the rotating ring and the non-rotating ring rotating in the forward direction. FIG. 5 is a pressure distribution diagram between the sealing surfaces in the state of FIG. 4, FIG. 6 is a simplified explanatory diagram showing the positional relationship between a rotating ring and a non-rotating ring rotating in opposite directions, FIG.
The figure is a pressure distribution diagram between the sealing surfaces in the state of FIG. M: two-way non-contact mechanical seal, P _O1 : dynamic pressure due to spiral groove having forward angle in forward rotation, P _O : total dynamic pressure in forward rotation, P _I1 : screw with forward angle in reverse rotation Dynamic pressure by line groove, P _I : Total dynamic pressure in reverse rotation, 1: Housing, 2: Rotary shaft, 3: Rotating ring, 4: Non-rotating ring, 5: Seal surface, 6: Seal surface, 7: Pressing Means, 8: spiral groove,
9: spiral groove, 10: fixed sleeve, 11: flange, 12: step, 13: fastening sleeve, 14: holding nut, 15: O-ring, 1
6: O-ring, 17: O-ring, 18: holding device, 19: step, 20: fixed sleeve, 21: O-ring, 22: sliding part, 23: O-ring, 24:
disk.

Claims (6)

(57) [Claims] 1. A rotary ring hermetically sealed to a rotating shaft and a non-rotating ring which is axially movable and hermetically mounted on a housing and axially urged by a pressing means. Extending with the peripheral edge or the inner peripheral edge as a base end, providing spiral grooves having a substantially mirror image relationship with each other with their ends closed, generating dynamic pressure in the spiral groove on one of the sealing surfaces with forward rotation of the rotating shaft, A two-way non-contact mechanical seal characterized in that a dynamic pressure is generated in a spiral groove on the other seal surface with rotation in the reverse direction. 2. The two-way non-contact mechanical seal according to claim 1, wherein a dam width ratio of said spiral groove is set to about 0.2 to 0.8. 3. The two-way non-contact mechanical seal according to claim 1, wherein the number of spiral grooves having an advancing angle with respect to the direction of relative rotation by forward rotation of the rotating shaft is set to be larger than the other. 4. The two-way non-contact mechanical seal according to claim 1, wherein the width of the spiral groove having an advancing angle with respect to the direction of relative rotation by the forward rotation of the rotating shaft is set wider than the other. 5. The two-way non-contact mechanical seal according to claim 1, wherein a depth of the spiral groove having an advancing angle with respect to a relative rotation direction by the forward rotation of the rotating shaft is set to be deeper than the other. . 6. The two-way non-contact mechanical seal according to claim 1, wherein the spiral grooves formed on both of the seal surfaces have a perfect mirror image relationship.