JPH0454382A - Non-contact mechanical seal - Google Patents

Abstract

PURPOSE:To restrain leakage of a sealed fluid to the minimum by way of heightening a peak value of dynamic pressure of either of helical groove groups by providing a plural number of kinds of helical grooves which are different from each other in length periodically in the circumferential direction on a sealed surface of either one of or both of a rotational ring and a non-rotational ring. CONSTITUTION:A non-contact mechanical seal M is provided with a rotational ring 3 sealed and fixed on a rotary shaft 2 and a non-rotational ring 4 sealed and installed in a housing 1, and it is alternately provided with short helical grooves 8 and long helical grooves 9 in the circumferential direction which are two kinds of the helical grooves extending inward from the outer peripheral edge of the rotational ring 3, having angles of advance in the relative rotational direction and different in length. A dumb breadth ratio of the short helical grooves 8 is set as about 0.2-0.5 and that of the long helical grooves 9 as about 0.5-0.8. The most suitable value of this dumb breadth ratio varies in accordance with another parameter, but as a more favorable value, the dumb breadth ratio of the short helical grooves 8 is about 0.3 and that of the long helical grooves about 0.6. Consequently, it is possible to restrain leakage of a sealed liquid to the minimum as the peak value of dynamic pressure of either of the helical groove groups becomes much higher than the time of normal driving.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the improvement of non-contact mechanical seals, and more specifically, to use under high circumferential speed conditions as shaft seal devices for fluid equipment such as gas turbines and compressors. Regarding non-contact mechanical seals.

[Conventional technology]

Conventionally, non-contact mechanical seals that seal between a rotating shaft and a housing in a compressor or the like have already been provided. For example, Japanese Patent Publication No. 1-22509 discloses, as shown in FIG. 10, a rotating ring a sealed and fixed to a rotating shaft, and a non-rotating ring b sealed and attached to a housing and urged in the axial direction by a pressing means. As shown in FIG. 12, a large number of spiral grooves d of the same length and having an advancing angle with respect to the relative rotation direction are formed on one of the seal surfaces C facing the seal surface C. Non-contact mechanical seals have been provided in which sealed fluid is pumped between sealing surfaces that are spaced apart.

Thereby, due to pressure fluctuations and temperature fluctuations, the rotating ring a
If the parallelism of the seal surfaces C is lost due to deformation of the non-rotating ring or the non-rotating ring, a couple is generated in the non-rotating ring B in the direction of making the seal surfaces parallel to each other, automatically maintaining a stable seal surface spacing. It can be adjusted to That is, the 10th
When the non-rotating ring b in the normal state shown by the dotted line in the figure deforms clockwise to the state shown by the solid line, the pressure decreases at the outer circumference (P+) and at the inner circumference as shown in Fig. 11. As the pressure increases (P2), a counterclockwise force couple C1 is generated in the non-rotating ring b by balance with a pressing means (not shown), so that the sealing surfaces can be self-aligned so that they are parallel to each other. In this case, the peak value of the pressure at the sealing surface decreases, resulting in a problem that the load capacity decreases and the gap becomes unstable during self-alignment.

[Problem to be solved by the invention]

In view of the above-mentioned situation, the present invention aims to solve the problem by force-feeding the sealed fluid to the sealing surface through a plurality of spiral groove groups with different lengths, and adjusting the peak value of the dynamic pressure on the sealing surface to different radial directions. They are formed at multiple positions to generate a self-aligning force couple against the deformation of the rotating ring or non-constant rotating ring, and are set so that the peak value of the dynamic pressure due to either spiral groove group becomes even larger. The purpose of this invention is to provide a non-contact mechanical seal.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention provides a structure in which a rotating ring that is sealed and fixed to a rotating shaft and a non-rotating ring that is movable in the axial direction and sealed in the housing and that is urged in the axial direction by a pressing means are brought into contact with each other. In a non-contact mechanical seal in which a spiral groove having an advancing angle with respect to the direction of relative rotation is provided on the sealing surface to force the sealed fluid between the sealing surfaces, either one or both of the rotating ring and the non-rotating ring A plurality of types of spiral grooves are periodically provided on the sealing surface in the circumferential direction, extending from the outer peripheral edge or the inner peripheral edge as the base end, having an advancing angle with respect to the relative rotation direction, and having different groove lengths. A non-contact mechanical seal has been constructed.

Further, two types of spiral grooves having different groove lengths are used as the end line groove, and the dam width ratio of one of the short carp line grooves is set to about 0.2 to 0.
5. The dam stop of the other long spiral groove was set to about 0.5 to 0.8.

Furthermore, two types of spiral grooves with different groove lengths were used, and the dam stop of one short spiral groove was set to approximately 0.3, and the dam width ratio of the other long spiral groove was set to approximately 0.6. .

Two types of spiral grooves having different groove lengths were provided alternately in the circumferential direction.

[Effect]

The non-contact mechanical seal of the present invention having the above-mentioned contents extends on the sealing surface of one or both of the rotating ring and the non-rotating ring, with the outer circumferential edge or the inner circumferential edge as the base end, and the non-contact mechanical seal extends with respect to the relative rotation direction. By periodically providing multiple types of spiral grooves with advancing angles and different lengths in the circumferential direction, a fluid transport effect is achieved by the relative rotation of each group of spiral grooves with different lengths. The sealed fluid is pumped between the seal surfaces to form a pressure distribution with peak values of dynamic pressure at different positions in the radial direction of the seal surface, and the parallelism of the seal surfaces due to the deformation of the rotating ring or non-rotating ring is thereby created. A force couple is generated in the non-rotating ring to correct the deviation from the ring, and at this time, the peak value of the dynamic pressure in either spiral groove group becomes even higher, minimizing the leakage of the sealed fluid. It suppresses it.

[Example] Next, the present invention will be further described in detail based on the example shown in the accompanying drawings.

FIG. 1 shows the overall structure of a non-contact mechanical seal M according to the present invention, which is provided between a housing 1 and a rotating shaft 2 passing through the 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 has the rotating shaft 2
A rotating ring 3 is hermetically fixed to the housing 1, and a non-rotating ring 4 is hermetically attached to the housing 1. are movable in the axial direction in a sealed state, and each sealing surface 5.6 is biased in the axial direction toward each other by a pressing means 7 associated with the housing 1. As shown in FIG. 2, there are two types of spiral grooves extending inward from the outer peripheral edge of the rotating ring 3 and having different lengths and having advancing angles with respect to the relative rotational direction, that is, short spiral grooves 8. Long spiral grooves 9 are provided alternately in the circumferential direction.

The rotating ring 3 is coaxially inserted into a fixed sleeve 10 that is coaxially inserted into the rotating shaft 2, and the sealing surface 5 is attached to a flange portion 11 extending from one end of the fixed sleeve 10.
The fixed sleeve I is rested on the opposite side thereof, and the flange portion 11 is rested on the stepped portion 12 formed on the rotating shaft 2.
By tightening the end of the fixing sleeve 10 and the fixing sleeve 13 fitted on the outer part of the fixing sleeve 10 with the holding nand 14 fitted to the rotating shaft 2, the fixing sleeve 10 is fixed to the rotating shaft 2, and the rotating shaft 2 and the flange are fixed together. between the rotating ring 3 and the fixed sleeve 10, and between the rotating ring 3 and the flange portion 11.
An O-ring 15° 16.17° is inserted between them to seal them.

The non-rotating ring 4 is movable in the axial direction and hermetically held at a predetermined position by an annular holding device 18 that is hermetically fixed to the housing 1, and is pressed against the sealing surface 5 of the rotary ring 3 by a pressing means 7. The sealing surface 6 of the non-rotating ring 4 is biased in the approaching direction. Here, the holding device 18 has one end of its outer periphery abutted against a stepped portion 19 of the housing l, and the other end abutted against a fixed sleeve 20 to restrict movement in the axial direction. An O-ring 21 is interposed between the outer periphery of the non-rotating ring 4, and an O-ring 23 is interposed between the outer periphery of the annular sliding portion 22 extending in the axial direction from the inner periphery and the inner periphery of the non-rotating ring 4. Rotating ring 4
is movable in the axial direction 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 whose one end is 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 biased in the direction of the rotating ring 3, so that a pressing force is always applied in the direction in which both sealing surfaces 5.6 approach each other.

It should be noted that the non-rotating ring 4 does not make complete zero contact during rotation, but rather slides against the rotating ring 3 due to contact resistance in the initial stage when the rotating shaft 2 starts rotating from a stationary state, so that the rotating shaft 2 remains constant. When the number of rotations exceeds the rotation speed, the seal surfaces 5.6 slip and the non-rotating ring 4 almost stops sliding, but this is due to the viscosity of the fluid interposed between the seal surfaces 5.6. The number of revolutions at which the motors almost stop differs. Moreover, it is also possible to completely prevent sliding at any time due to the pressure difference.

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

FIG. 2 shows an example of a spiral groove pattern formed on the sealing surface 5 of the rotary ring 3 of the present invention, and the pattern shown is a short spiral groove 8 and a long spiral groove a9. Type M spiral grooves are formed inward from the outer peripheral edge of the rotary ring 3 alternately in the circumferential direction at an advancing angle with respect to the relative rotational direction. It is flat.

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

Here, OD is the outer shape of the common part of the seal surfaces 5 and 6, and ID
is the inner diameter, GD is the diameter of the contour circle formed at the boundary between the groove area of the inclined groove and the flat area, GD is SGD in the case of the short spiral groove 8, and SGD in the case of the long spiral groove 9. The value of LGD is entered.

Equation (1) is a formula that is valid when the inclined groove is formed with the outer peripheral side of the sealing surface as the base end, and (2) is a formula that is valid when the inclined groove is formed with the inner peripheral side 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 this dam width ratio varies depending on other parameters, but as more preferable values, the dam width ratio of the short groove 18 is about 0.3, and the dam width ratio of the long spiral groove 9 is about 0.6. It is.

Further, the spiral groove in the present invention has a depth of about 2 to 15 μm, and its width and advance angle are determined by the sealing pressure of the sealed fluid, the rotation speed, etc. In this embodiment, the spiral groove is formed on the sealing surface 5 of the rotating ring 3, but in principle it can also be formed on the sealing surface 6 of the non-rotating ring 4, or even on both sealing surfaces 5. It is possible.

The method of forming the spiral groove on the surface of the sealing surface is to form a material such as tungsten carbide, silicon carbide, silicon nitride, alumina ceramic, or metal material into a predetermined shape, and then form a spiral groove on the surface that will become the sealing surface. The grooves are formed using chemical, physical, or electrochemical methods. For example, etching,
It can be formed by powder blasting and various plating treatments.

Note that the pattern of the spiral groove is not limited to that shown in FIG. 2, and various patterns may be employed. For example, as shown in FIG. 3, a basic pattern with two short spiral grooves 8 and one long spiral a9 is formed in the circumferential direction, or conversely, as shown in FIG. There is a basic pattern in which one groove 8 and two long spiral grooves 9 are formed in the circumferential direction, and as shown in FIG. There are some with different widths. Furthermore, a combination of the above patterns is also possible, and a combination of three or more types of spiral grooves with different groove lengths is also possible.

Next, in the non-contact mechanical seal M of this embodiment,
Since the non-rotating ring 4 is subjected to pressure on its inner circumference,
The balance is expressed as follows, where BD is the balance diameter, and the value is set to 0.5 to 1.5.

Therefore, when the rotating shaft 2 rotates at high speed, the rotating ring 3
The sealed fluid having a predetermined sealing pressure is pumped between the sealing surfaces 5 and 6 by short spiral grooves 8 and long spiral grooves 9 having an advancing angle with respect to the rotational direction, and thereby A dynamic pressure higher than the sealing pressure is generated on the inside and outside in the radial direction of the sealing surface (<near the end of the Vt line groove), and this dynamic pressure causes the non-rotating ring 4 to move in the axial direction against the pressing force of the pressing means 7. The sealing surfaces 5 and 7 move to a state where the dynamic pressure caused by the fluid and the pressing force of the pressing means 7 are balanced, that is, a non-contact state where there is a parallel gap between the sealing surfaces 5.6.

In this state, the sealed fluid flows between the sealing surfaces 5 and 6 between the rotating shaft 2 and the non-rotating ring 4, and leaks slightly to the atmosphere. Although this leakage is unavoidable in principle, the structure of the present invention, which consists of two types of spiral groove groups, short spiral grooves 8 and long spiral grooves 9, has separate internal and external sections in the radial direction of the sealing surface. Because the action forms a dynamic pressure peak, it has excellent sealing performance for the enclosed fluid. Naturally, if more types of spiral groove groups with different groove lengths are formed, the peak position of the dynamic pressure on the sealing surface increases accordingly. Here, although the dynamic pressure decreases at the beginning of startup when the rotational speed is low or just before stopping, the flat portions of each sealing surface 5.6 are in close contact with each other, so the amount of leakage of the sealed fluid is small.

In normal operating conditions, the non-rotating ring 4 is in the dotted line position shown in FIGS. 6 and 8, and in that state forms the pressure distribution shown in dotted lines in FIGS. 7 and 9, respectively. In this pressure distribution, the vertical axis corresponds to the position in the radial direction of the sealing surface, the distribution with the peak value at the top is due to the short-end groove 8, and the distribution with the peak value at the bottom is due to the long spiral groove 9. be.

Therefore, during operation, the non-rotating ring 4 deforms itself or deforms relative to the rotating ring 3 due to thermal fluctuations and pressure fluctuations, and the sealing surface 6 moves inward as shown by the solid line in FIG. As a result, the new pressure distribution becomes as shown by the solid line in FIG. Pressure P due to groove 8. , and P. 2 is generated, pressures Pit and Pi2 are generated by the long spiral groove 9, and a parallel force is set around the center of gravity W in the cross section of the non-rotating ring 4 by the resultant force of PCII and pH and the resultant force of Po2 and pH2. Counterclockwise couple C trying to return to position
4 occurs.

Furthermore, even when the sealing surface 6 bends outward, a clockwise couple C2 is generated which tends to return it to the parallel position, 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, the peak value of one of the dynamic pressures due to the short spiral groove 8 and the long spiral groove 9 decreases, but the other increases, so the overall pressure between the sealing surfaces 5 and 6 decreases. As a result, the amount of leakage of the sealed fluid can be extremely reduced (suppressed) compared to conventional spiral grooves of the same length.

〔Effect of the invention〕

According to the above-described non-contact mechanical seal of the present invention, the rotating ring is hermetically fixed to the rotating shaft, the non-rotating ring is movable in the axial direction and is sealed in the housing, and is urged in the axial direction by the 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 sealing surfaces facing each other to force the sealed fluid between the sealing surfaces, either a rotating ring or a non-rotating ring. Or, on both seal surfaces, multiple types of spiral grooves extending from the outer peripheral edge or the inner peripheral edge as the base end, having advancing angles with respect to the relative rotation direction, and having different groove lengths are periodically arranged in the circumferential direction. Since the spiral grooves have different lengths, the fluid transport effect caused by the relative rotation of each group allows the sealed fluid to be pumped between the seal surfaces, and dynamic pressure is applied to different positions in the radial direction of the seal surfaces. It goes without saying that it is possible to form a pressure distribution with a peak value, thereby generating a force couple in the non-rotating ring that corrects the deviation of the sealing surfaces from parallelism due to deformation of the non-rotating ring, etc. The peak value of the dynamic pressure in either spiral groove group becomes higher than that during normal operation, and leakage of the sealed fluid can be suppressed to a minimum.

Further, two types of spiral grooves having different groove lengths are used as the spiral groove, and the dam stop of one of the short spiral grooves is about 0.2 to 0.2 mm.
5. By setting the dam width ratio of the other long spiral groove to about 0.5 to 0.8, it is preferable that the dam width ratio of the short spiral groove is set to about 0.3 and the dam width ratio of the long spiral groove. By setting 0.6 to approximately 0.6, it is possible to generate peaks of dynamic pressure on the sealing surface in the radial direction inside and outside of the center of gravity in the cross section of the non-rotating ring. This allows for greater stability compared to longer lengths.

By providing two types of spiral grooves with different groove lengths alternately in the circumferential direction, the distribution of dynamic pressure in the circumferential direction can be made uniform.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the main part of the non-contact mechanical seal of the present invention installed between the rotating shaft and the housing, FIG. 2 is an end view showing an example of the spiral groove pattern of the present invention, and FIGS. Figure 5 is an end view showing another pattern of spiral grooves;
The figure is a simplified side view of the non-rotating ring deformed clockwise, Figure 7 is a pressure distribution diagram between the sealing surfaces in the state of Figure 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 surfaces in the state shown in Fig. 8, and Fig. 10 shows the non-contact mechanical seal in the conventional non-contact mechanical seal. A simplified side view of the rotating ring deformed clockwise, No. 11+Ff! J is a pressure distribution diagram between the seal surfaces in the state shown in FIG. 10, and FIG. 12 is an end view showing the same conventional spiral groove pattern. M: Non-contact mechanical seal, P O (+ P 02
'Pressure due to short spiral groove, P 11+ P 12'
Pressure due to long spiral groove, C1 + C2' couple, 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 helical groove, 9: Long helical groove, 10: Fixed sleeve, 11: Flange portion, 12: Step portion, 13: Fastening sleeve, 14: Holding nut, 15: O ring, 16
: O-ring, 17: O-ring, 18: Holding device, 19:
Stepped portion, 20: Fixed sleeve, 21: O-ring, 22: Sliding portion, 23: O-ring, 24: Disc.

Claims (1)

[Claims] 1) A rotary ring that is hermetically fixed to the rotary shaft and a non-rotating ring that is movable in the axial direction and is hermetically mounted on the housing and is urged in the axial direction by a pressing means. In a non-contact mechanical seal in which a spiral groove having an advancing angle with respect to the rotational direction is provided to force the sealed fluid between the sealing surfaces, the sealing surface of either or both of the rotating ring and the non-rotating ring includes: It is characterized by having multiple types of spiral grooves periodically provided in the circumferential direction, extending from the outer peripheral edge or the inner peripheral edge as the base end, having an advancing angle with respect to the relative rotation direction, and having different groove lengths. Non-contact mechanical seal. 2) Using two types of spiral grooves with different groove lengths, the dam width ratio of one short spiral groove is approximately 0.2 to 0.5, and the dam width ratio of the other long spiral groove is approximately 0. The non-contact mechanical seal according to claim 1, wherein the non-contact mechanical seal is set to .5 to 0.8. 3) Using two types of spiral grooves with different groove lengths, set the dam width ratio of one short spiral groove to approximately 0.3 and the dam width ratio of the other long spiral groove to approximately 0.6. The non-contact mechanical seal according to claim 1, comprising: 4) The non-contact mechanical seal according to claim 1, 2 or 3, wherein two types of spiral grooves having different groove lengths are provided alternately in the circumferential direction.