JPH0743037B2 - Non-contact mechanical seal - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a non-contact mechanical seal, and more specifically, it is used as a shaft sealing device for fluid equipment such as a gas turbine and a compressor under high peripheral speed conditions. A non-contact mechanical seal that does.

[Conventional technology]

Conventionally, a non-contact mechanical seal that seals between the housings of rotating shafts in compressors and the like has already been provided. For example, as shown in FIG. 10, Japanese Patent Publication No. 22509/1990 discloses a rotating ring a which is hermetically fixed to a rotating shaft and a non-rotating ring b which is hermetically mounted on a housing and axially biased by a pressing means. As shown in FIG. 12, a large number of spiral grooves d of the same length having an advancing angle with respect to the relative rotation direction are circumferentially arranged at regular intervals on one of the sealing surfaces c facing each other. There is provided a non-contact mechanical seal which is provided by and pressure-fed the enclosed object between the seal surfaces.

As a result, the rotating ring a due to pressure fluctuation and temperature fluctuation
When the non-rotating ring b is deformed and the parallelism of the sealing surface c is impaired, a couple force is generated in the non-rotating ring b in a direction in which the sealing surfaces are parallel to each other, and the sealing surface is automatically stable. It can be adjusted to the interval. That is, when the normal state non-rotating ring b shown by the dotted line in FIG. 10 is deformed clockwise to the state shown by the solid line, the pressure decreases at the outer peripheral portion as shown in FIG. 11 (P ₁ ). , The pressure increases in the inner peripheral part (P ₂ ), and counterclockwise couple C ₁ is generated in the non-rotating ring b by the balance with the pressing means (not shown) so that the sealing surfaces become parallel to each other. However, in this case, the peak value of the pressure on the sealing surface is reduced, so that the load capacity is reduced and the gap becomes unstable during self-alignment.

[Problems to be Solved by the Invention]

In view of the above-mentioned situation, the present invention is to solve the problem by pumping the enclosed fluid to the seal surface by a plurality of types of spiral groove groups having different lengths, and changing the peak value of the dynamic pressure on the seal surface in the radial direction. It was formed at multiple positions and generated a couple force that self-aligns against the deformation of the rotating ring and non-constant rotating ring, and was set so that the peak value of the dynamic pressure by any one of the spiral groove groups would be further increased. The point is to provide a non-contact mechanical seal.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, the present invention makes contact with a rotating ring that is hermetically fixed on a rotating shaft and a non-rotating ring that is axially movable and hermetically mounted on a housing and is axially biased by a pressing means. In a non-contact mechanical seal in which a spiral groove having an advancing angle with respect to the relative rotation direction is provided on the seal surface and the enclosed fluid is pressure-fed between the seal surfaces, either one or both of the rotating ring and the non-rotating ring is used. The sealing surface has two types of spiral grooves that extend with the outer peripheral edge or the inner peripheral edge as the base end and have an advancing angle with respect to the relative rotation direction, and have the same groove depth and different groove lengths. Periodically provided in the circumferential direction, the dam width ratio of one short spiral groove is set to about 0.2 to 0.5, and the dam width ratio of the other long spiral groove is set to about 0.5 to 0.8. A seal with each peak value of generated dynamic pressure at a dam width ratio of 0.5 Of set radially inner and outer positions different and constitute a non-contact mechanical seal a couple to correct a deviation from the parallel sealing surfaces due to the deformation of the rotating ring and non-rotating ring made by generating a non-rotating ring.

Further, two kinds of spiral grooves having different groove lengths were used, and the dam width ratio of one short spiral groove was set to about 0.3 and the dam width ratio of the other long spiral groove was set to about 0.6.

Then, two kinds of spiral grooves having different groove lengths were alternately provided in the circumferential direction.

[Action]

The non-contact mechanical seal of the present invention having the above contents, when the rotating ring rotates with respect to the non-rotating ring,
The enclosed fluid is pumped between the sealing surfaces by the relative rotation of each of the two types of spiral groove groups having an advancing angle with respect to the relative rotation direction and having the same groove depth and different groove lengths. , A dynamic pressure is generated between the sealing surfaces to form a non-contact state for sealing, and the dam width ratio of one spiral groove is about 0.2 to 0.5, and the dam width ratio of the other long spiral groove is About 0.5
Set to ~ 0.8 and each peak value of the dynamic pressure generated by the long and short spiral groove groups is set to different positions inside and outside the radial direction of the seal surface with the dam width ratio of 0.5 as a boundary to form a unique pressure distribution As a result, a couple force that corrects the deviation of the seal surface from being parallel due to the deformation of the rotating ring or the non-rotating ring is generated in the non-rotating ring. That is, when the gap between both seal surfaces in the non-contact state is sandwiched on the outer side in the radial direction due to the deformation of the rotating ring or the non-rotating ring during operation, the spiral groove group having the end on the outer side in the radial direction moves When the peak value of pressure increases, a couple force is generated in the non-rotating ring in the direction to widen the outer part of the gap. The peak value of the dynamic pressure increases, and the non-rotating ring has a self-aligning function of generating a couple in the direction to widen the inner portion of the gap, thereby minimizing leakage of the enclosed object.

〔Example〕

Next, the details of the present invention will be described based on the embodiments shown in the accompanying drawings.

FIG. 1 shows an overall structure of a non-contact mechanical seal M according to the present invention, which is provided between a housing 1 and a rotary shaft 2 penetrating an open end of the housing 1. Here, in the figure, A indicates the atmospheric pressure (low pressure) side, and B indicates the high pressure (seal pressure) side.

The non-contact mechanical seal M of this embodiment is the rotary shaft 2
A rotary ring 3 hermetically fixed to the housing 1 and a non-rotating ring 4 hermetically mounted on the housing 1, the sealing surfaces 5 and 6 of the rotary ring 3 and the non-rotating ring 4 are in contact with each other, and the non-rotating ring 4 Is movable in the sealed state in the axial direction, and is urged in the axial direction by the pressing means 7 associated with the housing 1 so that the respective seal surfaces 5 and 6 approach each other. And the second
As shown in the figure, two kinds of spiral grooves extending inward from the outer peripheral edge of the rotary ring 3 and having an advancing angle with respect to the relative rotation direction and having different lengths, that is, a short spiral groove 8 and a long spiral groove. 9 are provided alternately in the circumferential direction.

The rotating ring 3 is coaxially externally inserted into a fixed sleeve 10 which is coaxially externally inserted into the rotary shaft 2, and the fixed sleeve 10
A flange portion 11 extending from one end of the fixing sleeve 10 against the side opposite to the sealing surface 5, and the flange portion 11 against the step portion 12 formed on the rotary shaft 2 while being fitted onto the fixed sleeve 10. The fixing sleeve 10 and the fixed sleeve 10 are fixed to the rotary shaft together with the fixed sleeve 10 by tightening the ends of the fixed sleeve 10 with a retaining nut 14 screwed to the rotary shaft 2, and between the rotary shaft 2 and the flange portion 11 and the rotary ring 3. And the fixed sleeve 10 and between the rotary ring 3 and the flange portion 11, respectively, O-rings 15, 16, 17
Is installed and sealed.

The non-rotating ring 4 is axially movable to a predetermined position by an annular holding device 18 which is hermetically fixed to the housing 1 so as to hermetically hold the non-rotating ring 4, and the sealing surface 5 of the rotating ring 3 is pressed by a pressing means 7. The seal surface 6 of the non-rotating ring 4 is urged in the approaching direction. Here, the holding device 18 has one outer peripheral end abutting against the stepped portion 19 of the housing 1 and the other end abutting against the fixed sleeve 20 to restrict axial movement, and further, the housing 1 and the holding device 18 An O-ring 21 is interposed between the outer periphery of the non-rotating ring 4 and the outer periphery of an annular sliding portion 22 extending axially from the inner periphery of the non-rotating ring 4.
The ring 23 is interposed so that the non-rotating ring 4 is axially movable in a sealed state. Then, the other end of the pressing means 7, which is made of an elastic member such as a plurality of coil springs and has 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 the annular disc 24. In this case, the non-rotating ring 4 is elastically biased toward the rotating ring 3 so that the pressing force always acts in the direction in which the two sealing surfaces 5 and 6 approach each other.

It should be noted that the non-rotating ring 4 does not come into complete contact during rotation, but the rotating shaft 2 starts rotating from a stationary state and slides on the rotating ring 3 due to contact resistance in the initial stage, causing the rotating shaft 2 to rotate at a constant speed. If the number exceeds the limit, the sealing surface of each other
Since 5 and 6 slip, the non-rotating ring 4 almost stops sliding,
The number of rotations at which the sliding substantially stops depends on the viscosity of the fluid interposed between the seal surfaces 5 and 6. Further, it is possible to prevent the slide from completely sliding at any time due to the pressure difference.

Further, in the present embodiment, an example of the non-contact mechanical seal M including a pair of the rotating ring 3 and the non-rotating ring 4 is shown.
It is also possible to employ a tandem type in which a plurality of these are used and arranged in relation to each other in the axial direction.

FIG. 2 shows an example of a spiral groove pattern formed on the seal surface 5 of the rotating ring 3 of the present invention. The drawing shows two kinds of spiral grooves, a short spiral groove flow spiral groove 9 and a rotating ring. 3 is formed inwardly from the outer peripheral edge of the outer peripheral edge 3 in the relative rotational direction and is alternately formed in the circumferential direction, and the seal surface having no spiral groove is flat.

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, GD is the direct line of the contour circle formed at the boundary between the groove area and the flat area of the spiral groove, and GD is the short spiral line. SG for groove 8
In the case of D and the long spiral groove 9, the value of LGD is entered.

Formula (1) is a formula applied when the spiral groove is formed with the outer peripheral side of the seal surface as the base end, and (2) is a formula applied when the inner peripheral side is formed as the base end. In the present invention, the dam width ratio of the short spiral groove 8 is set to about 0.2 to 0.5, and the dam width ratio of the long spiral groove 9 is set to about 0.5 to 0.8. The optimum value of the dam width ratio varies depending on other parameters, but more preferable values are a dam width ratio of the short spiral groove 8 of about 0.3 and a dam width ratio of the long spiral groove 9 of about 0.6.

Further, the spiral groove in the present invention has a depth of about 2 to 15 μm, and the width and the angle of the advance angle are determined by the sealing pressure and the rotation speed of the enclosed fluid. Although the spiral groove is formed on the seal surface 5 of the rotating ring 3 in this embodiment, it is theoretically possible to form the spiral groove on the seal surface 6 of the non-rotating ring 4 or on both seal surfaces 5 and 6. Is possible.

Then, the method of forming the spiral groove on the surface of the sealing surface is as follows: after forming the spiral groove into a predetermined shape with a material such as tungsten carbide, silicon carbide, silicon nitride, alumina ceramics, and a metal material,
Spiral grooves are formed on the surface to be the sealing surface by a chemical, physical or electrochemical method. For example, it can be formed by etching, powder blasting, and various plating treatments.

The spiral groove pattern is not limited to that shown in FIG. 2, and various patterns can be adopted. For example, as shown in FIG. 3, a basic pattern in which two short spiral grooves 8 and one long spiral groove 9 are formed in the circumferential direction, or conversely, as shown in FIG. A basic pattern having one wire groove 8 and two long spiral grooves 9 is formed in the circumferential direction, and as shown in FIG. 5, a short spiral groove 8 and a long spiral groove 9 are formed. Some have different groove widths. Further, a combination of the above patterns is also possible, and a combination with three or more types of spiral grooves having different groove lengths is also possible.

Next, in the non-contact mechanical seal M of this embodiment,
Since the non-rotating ring 4 receives pressure on its inner circumference,
For the balance, if BD is the balance diameter, The value is set to 0.5 to 1.5.

When the rotary shaft 2 rotates at a high speed, the rotary ring 3
The short spiral groove 8 and the long spiral groove 9 having an advancing angle with respect to the rotational direction formed on the sealing surface 5 of the seal fluid 5 pumps the enclosed fluid having a predetermined sealing pressure between the sealing surfaces 5 and 6, thereby Dynamic pressure higher than the seal pressure is generated inside and outside (near the end of the spiral groove) in the radial direction of the sealing surface, and the dynamic pressure causes the non-rotating ring 4 to resist the pressing force of the pressing means 7 in the axial direction. To the non-contact state having a parallel gap between the seal surfaces 5 and 6, that is, the dynamic pressure by the fluid and the pressing force of the pressing means 7 are balanced. In this state, the sealed fluid flows from between the sealing surfaces 5 and 6 to the rotating shaft 2 and the non-rotating ring 4
And a slight leak to the atmosphere side. Although this leakage is unavoidable in principle, the two spiral groove groups of the short spiral groove 8 and the long spiral groove 9 according to the present invention are provided inside and outside the sealing surface in the radial direction. Since the peak of the dynamic pressure is formed by the action, the sealing property of the enclosed fluid is excellent. Naturally, when more types of spiral groove groups having different groove lengths are formed, the peak position of the dynamic pressure on the seal surface increases accordingly. Here, the dynamic pressure decreases at the beginning of the engine at a low rotation speed or immediately before the stop, but the sealing surfaces 5, 6
Since the flat portions of the above are in close contact with each other, the leakage amount of the enclosed fluid is small.

In a normal operating condition, the non-rotating ring 4 is in the dotted position shown in FIGS. 6 and 8, and in that condition the pressure distributions shown by dotted lines in FIGS. 7 and 9 are formed. In this pressure distribution, the vertical axis corresponds to the radial position of the seal surface, the distribution having the peak value at the upper portion is the short spiral groove 8, and the distribution having the peak value at the lower portion is the long spiral groove 9.
It is due to.

Therefore, during operation, the non-rotating ring 4 deforms itself due to thermal fluctuation or pressure fluctuation or relatively deforms with respect to the rotating ring 3, so that the sealing surface 6 moves inward as shown by the solid line in FIG. If it bends, as a result, the new pressure distribution becomes as shown by the solid line in FIG. 7, and the action of the dynamic pressure and the pressing force of the pressing means 7 causes a short spiral line inside and outside the sealing surface 6 in the radial direction. Grooves 8 generate pressures P ₀₁ and P ₀₂ ,
Pressures P ₁₁ and P ₁₂ are generated by the long spiral groove 9, and are set around the center of gravity W in the cross section of the non-rotating ring 4 by the resultant force of P ₀₁ and P _{11 and} the resultant force of P ₀₂ and P ₁₂ . A counterclockwise couple C ₁ that tries to return to the parallel position is generated.

Also, when the sealing surface 6 is bent outward, a clockwise couple C ₂ that tries to return it to the parallel position is generated as shown in FIGS. 8 and 9.

Here, as shown in FIGS. 7 and 9, the non-rotating ring 4
Due to the deformation of the sealing surface 6 of the above, one peak value of the dynamic pressure by the short spiral groove 8 and the long spiral groove 9 decreases, but the other increases, conversely, the total pressure between the sealing surfaces 5 and 6 increases. Does not occur, and as a result, the amount of leakage of the enclosed fluid can be suppressed to an extremely small amount as compared with the conventional one using the spiral groove of the same length.

〔The invention's effect〕

According to the non-contact mechanical seal of the present invention as described above, a rotating ring hermetically fixed to a rotating shaft and a non-rotating ring which is axially movable and hermetically mounted in a housing and axially biased by a pressing means. In a non-contact mechanical seal in which a spiral groove having an advancing angle with respect to the relative rotation direction is provided on the seal surfaces facing each other, and a sealed fluid is pumped between the seal surfaces, one of the non-rotating rings of the rotating ring Or, on both seal surfaces, two types of spiral wires that extend with their outer peripheral edge or inner peripheral edge as a base end and have an advancing angle with respect to the relative rotation direction, and have the same groove depth and different groove lengths The grooves are periodically provided in the circumferential direction, and the dam width ratio of one short spiral groove is about 0.2 to 0.5, and the dam width ratio of the other long spiral groove is about 0.
2 to 0.5, and the dam width ratio of the other long spiral groove is set to about 0.5 to 0.8, and the peak value of the dynamic pressure generated by the long and short spiral groove groups is set as the boundary of the dam width ratio of 0.5. Since the non-rotating ring is set to different positions inside and outside in the radial direction and a couple of forces that correct the deviation of the seal surface from being parallel due to the deformation of the rotating ring and the non-rotating ring are generated, The sealed fluid is pumped between the seal faces by the fluid transport action due to the relative rotation of the spiral groove group, and the dynamic pressure can keep both seal faces in a non-contact state at the time of high speed rotation. By forming a pressure distribution with a dynamic pressure peak value by each spiral groove group at different positions in the radial direction inside and outside of the seal surface with 0.5 as a boundary, it is possible to change the parallelism of the seal surface due to deformation of the non-rotating ring etc. Non-rotating couple to correct gap It has an excellent self-alignment function that can be generated in the ring and automatically adjusts the parallelism of both seal faces, and when the seal faces deviate from parallel, one of the spiral groove groups The peak value of the dynamic pressure becomes higher than that during normal operation, and the leakage of the enclosed fluid can be suppressed to a minimum.

Also, depending on the position of the center of gravity in the cross section of the non-rotating ring, by setting the dam width ratio of the short spiral groove to about 0.3 and the dam width ratio of the long spiral groove to about 0.6, It is possible to form a pressure distribution having the peak value of dynamic pressure of both long and short spiral groove groups on the outside in the radial direction, and the peak value of dynamic pressure of one spiral groove group increases due to deviation of the seal surface from parallel. However, the peak value of the dynamic pressure of the other spiral groove group decreases, and the couple generated in the non-rotating ring when the pressure balance is disrupted effectively acts around the center of gravity, and the sealing surface is parallel to the fast Return to the state.

Further, the two types of spiral grooves having different groove lengths are alternately provided in the circumferential direction, so that the dynamic pressure distribution in the circumferential direction can be made uniform.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a state in which a non-contact mechanical seal of the present invention is mounted between a rotary shaft and a housing, FIG. 2 is an end view showing an example of a spiral groove pattern of the present invention, and FIGS. FIG. 5 is an end view showing another pattern of the spiral groove, FIG.
The figure shows a simplified side view of the non-rotating ring deformed clockwise, and Fig. 7 shows the pressure distribution between the seal faces in the state of Fig. 6,
FIG. 8 is a simplified side view of the non-rotating ring deformed counterclockwise, FIG. 9 is a pressure distribution diagram between the seal faces in the state of FIG. 8, and FIG. 10 is a conventional non-contact mechanical seal. A simplified side view of the non-rotating ring deformed clockwise, FIG. 11 is a pressure distribution diagram between the sealing surfaces in the state of FIG. 10,
FIG. 12 is also an end view showing a conventional spiral groove pattern. M: Non-contact mechanical seal, P ₀₁ , P ₀₂ : Pressure due to short spiral groove, P ₁₁ , P ₁₂ : Pressure due to long spiral groove, C ₁ , C ₂ : Coupling force, W: Center of gravity in cross section, 1: Housing, 2: rotating shaft, 3: rotating ring, 4: non-rotating ring, 5: sealing surface, 6: sealing surface, 7: pressing means, 8: short spiral groove, 9: long spiral groove, 10: fixed Sleeve, 11:
Flange, 12: Step, 13: Fastening sleeve, 14: Holding nut, 15: O-ring, 16: O-ring, 17: O-ring, 18: Holding device, 19: Step, 20: Fixed sleeve, 21 : O-ring, 22: sliding part, 23: O-ring, 24: disc.

Claims (3)

[Claims] 1. A relative rotation direction to a seal surface which is in contact with a non-rotating ring which is axially movable and hermetically mounted in a housing of a rotating ring which is hermetically fixed to a rotating shaft and which is axially urged by a pressing means. In a non-contact mechanical seal in which a spiral groove having an advancing angle is provided and the enclosed fluid is pumped between the seal surfaces, either the rotating ring or the non-rotating ring, or both sealing surfaces, Two types of spiral grooves that extend from the peripheral edge or the inner peripheral edge as a base end and have an advancing angle with respect to the relative rotation direction and that have the same groove depth and different groove lengths are periodically arranged in the circumferential direction. By setting the dam width ratio of one short spiral groove to approximately 0.2 to 0.5 and the dam width ratio of the other long spiral groove to approximately 0.5 to 0.8, the dynamic pressure generated by the long and short spiral groove groups can be adjusted. The peak value is different between inside and outside in the radial direction of the sealing surface with a dam width ratio of 0.5. Set the position, the non-contact mechanical seal, characterized by comprising by generating couple to correct a deviation from the parallel sealing surfaces due to the deformation of the rotating ring and non-rotating ring in a non-rotating ring. 2. The non-contact mechanical seal according to claim 1, wherein the dam width ratio of the one short spiral groove is set to about 0.3 and the dam width ratio of the other long spiral groove is set to about 0.6. 3. The non-contact mechanical seal according to claim 1 or 2, wherein two types of spiral grooves having different groove lengths are alternately provided in the circumferential direction.