JPH08312791A - Mechanical seal - Google Patents

Abstract

PURPOSE: To provide a mechanical seal to prevent the occurrence of unstable phenomenon wherein the gas in an axial direction of a shaft seal surface is widely opened. CONSTITUTION: A corrugated groove 113 having a waveform formed in an outer peripheral edge to lengthen a peripheral edge length is formed on at the inner peripheral side of at least one of the rear end face of a rotary ring forming a shaft seal surface and the front end face of a fixed ring 102. The area of a flow passage on the boundary line of an outlet from a gap to a low pressure chamber is increased, choke is prevented from occurring, the increase of a pressure in the vicinity of the boundary is decreased, and a trouble is prevented from occurring. Further, a mechanical seal is applied to sealing of a shaft seal part having a high pressure ratio between a high pressure chamber and a low pressure chamber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanical seal for preventing fluid from leaking from a shaft seal portion of a rotary shaft, and more particularly to a mechanical seal used for a shaft seal portion of a high pressure rotating machine such as a gas compressor.

[0002]

2. Description of the Related Art FIG. 6 is a longitudinal sectional view showing an example of a mechanical seal conventionally used in a gas compressor, FIG.
FIG. 4 is a partial front view showing a shaft sealing surface (sliding surface) provided on the front end surface of the fixed ring 2.

As shown in these drawings, the mechanical seal is formed between the high pressure chamber 3 and the low pressure chamber 4 formed by the outer peripheral surface of the rotary shaft 5 and the inner peripheral surface of a casing 8 surrounding the rotary shaft 5. The rear end surface of the rotary ring 1 fixed to the outer peripheral surface of the rotary shaft 5 by a pair of shaft sleeves 6 and 7, the seal housing 9 fitted and inserted in the inner peripheral surface of the casing 8, and the rear end of the seal housing 9 and the spring. A fixed ring 2 which is attached via 10 and is attached via a support ring 11 which moves back and forth inside the seal housing 9 and which is biased to the rear end surface of the rotary ring 1 by the elastic force of the spring 10. Sealing is performed by a so-called annular shaft sealing surface, which is a gap in the axial direction formed by the front end face of the. Then, in such a mechanical seal, from the high pressure chamber 3 to the rotating ring 1 and the fixed ring 2
In order to reduce the leakage amount of the fluid that flows through the axial gap (hereinafter, simply referred to as a gap) formed between and to the low pressure chamber 4, it is necessary to keep the gap small and stable. .

Therefore, an annular circumferential groove 11 is provided on the shaft sealing surface at the front end of the fixed ring 2 shown in FIG.
A plurality of communication holes 12 for radially communicating the inside of the circumferential groove 11 with the high pressure chamber 3 on the outer circumference of the fixed ring 2 are provided inside the fixed ring 2 in the circumferential direction. Further, as shown in FIG. 6, the rotary shaft 5 is provided on the shaft sealing surface of the rear end surface of the rotary ring 1.
Due to the rotation, a plurality of spiral grooves 31 are provided in the circumferential direction for transferring the fluid in the circumferential groove 11 of the fixed ring 2 flowing from the high pressure chamber 3 through the communication hole 12 toward the high pressure chamber 3 side. There is.

By thus forming the shaft sealing surface of the mechanical seal, the rotation of the rotary shaft 5 causes the rotary ring 1 to rotate.
By the plurality of spiral grooves 31 provided on the shaft sealing surface of
The fluid pressure generated by transferring the fluid in the circumferential groove 11 of the fixed ring 2 to the high pressure chamber 3 side and the low pressure chamber from the circumferential groove 11 of the fixed ring 2 through the gap between the rings 1 and 2. Four
The fluid pressure flowing in acts on the shaft sealing surface formed between the rear end surface of the rotating ring 1 and the front end surface of the fixed ring 2 to prevent contact between the rear end surface of the rotating ring 1 and the front end surface of the fixed ring 2. I am trying to do it.

That is, since the fluid pressure generated in the spiral groove 31 of the rotating ring 1 changes depending on the size of the gap between the rotating ring 1 and the fixed ring 2, the fixed ring 2
The fixed ring 2 moves in the axial direction so that the sum of the fluid force of the rear surface acting on the spring and the force of the spring 10 becomes equal to the sum of the fluid force generated in the shaft sealing surface gap, and the rotating ring 1 and the fixed ring 2 are moved. A gap of an appropriate size is maintained in the axial direction of the shaft-sealing surface.

In particular, in the spiral groove 31 provided on the rotary ring 4 in the circumferential direction, the fluid introduced from the circumferential groove 11 to the high-pressure side of the rotary ring 1 as the rotary shaft 5 rotates,
When the pressure is hydrodynamically increased and the gap is small, the pressure becomes large, so-called film rigidity is maintained, so that the size of the gap is kept stable and the contact between the rings 1 and 2 is prevented.

However, when the pressure in the high pressure chamber 3 increases and the pressure difference from the pressure in the low pressure chamber 4 increases, when the fluid flows from the high pressure chamber 3 to the low pressure chamber 4, in the gap between the rings 1 and 2, It becomes the speed of sound and chokes. As a result, the pressure on the boundary line of the low pressure chamber 4 becomes high. Further, in such a state, when the gap becomes large, the viscous resistance of the flow in the gap becomes relatively small, and the pressure on the boundary line of the low pressure chamber 4 tends to become higher. This means that when the gap becomes large,
The so-called film rigidity, which increases the film pressure, has a negative value, and when the gap exceeds a certain value, there is a disadvantage that an unstable phenomenon of opening the mouth at once occurs.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the conventional mechanical seal, the present invention provides a notch on the inner peripheral surface of the rotary ring or the fixed ring, and provides a cutout between the rotary ring and the fixed ring. Shaft sealing surface The area of the flow path on the boundary line formed between the gap and the low pressure chamber is made wavy on the boundary line of the portion opening to the low pressure chamber from the gap in the axial direction, and the circumferential length on the boundary line is lengthened. It is an object of the present invention to provide a mechanical seal in which chokes are prevented by increasing the flow velocity to reduce the flow velocity.

[0010]

Therefore, the mechanical seal of the present invention has the following means. The rear end surface of the rotating ring forming the shaft sealing surface between the high pressure chamber and the low pressure chamber formed on the outer peripheral surface of the rotating shaft, or the front end surface of the fixed ring, on the inner peripheral side opening to at least one of the low pressure chambers, A corrugated groove having a corrugated peripheral edge is provided to make the inner peripheral length longer. The shape of the corrugated groove is preferably such that the length of the peripheral edge of the corrugated groove is 20% or more longer than the inner peripheral length of the shaft sealing surface when the corrugated groove is not provided. Further, the waveform of the corrugated groove may be formed by a straight line or an arc.

[0011]

According to the mechanical seal of the present invention, the shape of the boundary line between the rotary ring opening to the low pressure chamber or the inner circumference side of the fixed ring, that is, the boundary line between the gap and the low pressure chamber is corrugated by the above-mentioned means. By this, the circumference of the boundary line with the low pressure chamber can be lengthened, and the area of the outlet flow path from the shaft sealing surface formed by the rear end surface of the rotating ring and the front end surface of the fixed ring to the low pressure chamber increases, and Even if the pressure on the side is made higher, it is possible to prevent the choke phenomenon that occurs on the boundary line on the low pressure side and stabilize the size of the shaft sealing surface gap. Further, the pressure of the high-pressure chamber can be selected within a range that does not choke according to the circumference of the boundary line, which is effective for increasing the pressure of the high-pressure chamber.

[0012]

Embodiments of the mechanical seal of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of an embodiment of the mechanical seal of the present invention.

As shown in the figure, a high pressure chamber 3 and a low pressure chamber 4 are formed between the outer peripheral surface of the rotary shaft 5 and the inner peripheral surface of a casing 8 surrounding the rotary shaft 5. Further, on the outer peripheral surface of the rotary shaft 5, the rotary ring 1 is fixed to the outer peripheral surface of the rotary shaft 5 by a pair of shaft sleeves 6 and 7, and is projected. The front end face of the rotary ring 1 is connected to the shaft sleeve 6 via the rotation stopper 21 and the seal ring 17, and the rear end face is inclined in the rotational direction as shown in FIG. A plurality of spiral grooves 31 that are recessed in the radial direction and that are open at the outer peripheral edge are provided.

Further, a seal housing is fitted and inserted into the inner peripheral surface of the casing 8 via a seal ring 16, the rear end of which is fixed to the casing 8 by a bolt 25, and the rear end portion of which is protruded from the inner peripheral surface of the casing 8. 9 is provided. The rotation stopper 2 interposed between the seal housing 9 and the protruding portion
3, a seal ring 20 is provided, the rear end surface is connected by a spring 10, and a support ring 32 is provided that can move back and forth in the seal ring 9 in the axial direction of the rotating shaft 5. The fixed ring 102 is connected to the front end surface of the support ring 32 via a rotation stopper 34 and a seal ring 32.

As shown in FIG. 3, an annular circumferential groove 111 is provided on the front end surface of the fixing ring 102, and the circumferential groove 111 and the high pressure chamber 3 on the outer peripheral surface are communicated with each other. A plurality of communication holes 112 are formed in the radial direction. Further, on the inner peripheral side of the fixing ring 102, that is, on the front end surface on the inner surface side facing the low pressure chamber 4, as shown in FIG. 3 and FIG. 4 which is a detailed view of a portion A of FIG. The corrugated groove 113 formed is recessed. Unlike the present embodiment, the corrugated groove 113 may be provided on the inner peripheral side of the rear end of the rotary ring 1. A stopper 24 is provided on the inner peripheral surface of the seal housing 9 so as to stop the fixed ring 102 from advancing excessively.

As described above, the front end of the fixed ring 2 is pushed toward the rotary ring 1 by the rear end surface of the rotary ring 1 fixed to the rotary shaft 5 and the spring 10 attached to the casing 8 surrounding the rotary shaft 5. Form a shaft sealing surface with the surface,
In a mechanical seal formed with a shaft sealing surface for sealing between the high pressure chamber 3 and the low pressure chamber 4, the rear end surface of the rotary ring 1 is opened to the high pressure chamber 3, and the rotation of the rotary ring 1 sucks high pressure gas. Multiple spiral groove 3
1 and having a rotating ring 1 or a fixed ring 2,
A plurality of corrugated grooves 113 opening to the low pressure chamber 4 are provided on at least one of the facing surfaces, and the pressure of the corrugated grooves 113 is set to a depth that is substantially equal to the pressure of the low pressure chamber 4. The peripheral length of the low-pressure chamber 4 formed by the inner periphery of the gap and the outer periphery of the corrugated groove 113 is longer than the peripheral peripheral length when the corrugated groove 113 is not provided. Further, this peripheral edge length is 20% of the peripheral edge length when the corrugated groove 113 is not provided.
It is preferable to form the waveform so as to be longer than the above.

Therefore, when the gas flows from the high-pressure chamber 3 to the low-pressure chamber 4 in the narrow gap formed in the shaft-sealing surface and when the pressure gradually decreases due to the viscosity of the gas, when the pressure decreases, Since the specific volume of the gas becomes large, the flow velocity becomes large toward the low pressure side. Further, as the pressure ratio between the high-pressure chamber 3 and the low-pressure chamber 4 increases, the speed ratio between the inlet where the gas flows into the gap and the outlet where the gas flows out to the low-pressure chamber 4 also increases. When the amount of leakage is small, the flow velocity at the outlet to the low pressure chamber 4 does not reach the speed of sound, and the choke phenomenon or the instability phenomenon of the gap does not occur.

When the pressure ratio between the high pressure chamber 3 and the low pressure chamber 4 becomes large and the gap becomes large, a corrugated groove 113 having an infinite number of corrugations is provided on the inner peripheral side front end face of the fixed ring 102. , The shape of the boundary line between the gap and the low pressure chamber 4 is corrugated, and further, in the axial direction such that the pressure on this boundary line is almost the same as that of the low pressure chamber 4, as a wavy shape with sufficient depth, By increasing the circumference of the boundary between the low-pressure chamber 4 and the gap, the flow passage area can be increased and the flow velocity can be reduced, and the flow velocity on the boundary line does not reach the sonic velocity. Because the flow velocity at the outlet is reduced, the pressure distribution that occurs when taper is applied so that the gap at the outlet is increased, which makes hydrostatic instability, so-called negative film rigidity. The phenomenon of gap instability does not occur.

Next, FIG. 5 is a view showing a second embodiment of the present invention. Instead of the corrugated groove 113 having a linear outer peripheral edge shown in FIG. A corrugated groove 213 is formed by providing an arcuate notch on the outer peripheral edge.
The corrugated groove 213 of this embodiment has an advantage that it can be relatively easily machined by a drilling machine or the like as a means for increasing the length of the low pressure side boundary line. The action and effect are
Same as the embodiment.

[0020]

As described above, according to the mechanical seal of the present invention, the mechanical seal according to the claims
The streamline near the boundary line between the low pressure chamber and the axial gap of the shaft sealing surface formed by the rear end surface of the rotating ring and the front end surface of the fixed ring is
As shown in FIG. 4, in the vicinity of the boundary line, the streamline has a divergent shape and the flow path becomes wider, and as a result, the flow velocity becomes smaller. For this reason, the fluid flowing through the shaft sealing surface has a large specific volume along the streamline, so that the maximum flow velocity is naturally on the boundary line, but the flow passage area on the boundary line is large and the high-pressure chamber side Even if the pressure is increased, the choke phenomenon can be prevented from occurring and the size of the gap can be stabilized.

On the contrary, by increasing the circumferential length on the boundary line, the pressure in the high pressure chamber in the non-choke range can be increased, so that the high pressure chamber and the low pressure chamber having a large pressure difference can be sealed.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a mechanical seal of the present invention,

FIG. 2 is a front view showing a shaft sealing surface of the rotating ring shown in FIG.

3 is a front view showing a shaft sealing surface of the fixing ring shown in FIG.

FIG. 4 is a diagram showing details of a portion A of FIG. 3 and a flow in a gap of a shaft sealing portion,

FIG. 5 is a front view of a shaft sealing surface of a fixing ring showing a second embodiment of the present invention,

FIG. 6 is a longitudinal sectional view showing a conventional mechanical seal,

FIG. 7 is a front view showing a shaft sealing surface of a conventional fixing ring.

[Explanation of symbols]

 1 rotating ring 3 high pressure chamber 4 low pressure chamber 5 rotating shaft 6 shaft sleeve 7 shaft sleeve 8 casing 9 seal housing 10 spring 16, 17, 20, 23 seal ring 21, 23, 34 whirl stop 24 stopper 25 bolt 31 spiral groove 32 support Rings 102, 202 Fixed rings 111, 211 Circumferential grooves 112 Communication holes 113, 213 Corrugated grooves

Claims (1)

[Claims] 1. A rotary ring fixed to the outer peripheral surface of a rotary shaft, the rear end surface of which has a plurality of spiral grooves radially provided in a high pressure chamber formed on the outer peripheral surface of the rotary shaft, and the rotary shaft. A ring-shaped circumferential groove, which is attached to the inner circumference of the surrounding casing with a spring interposed and has an inner circumferential end of the spiral groove opened, is provided on the front end surface, and the circumferential groove communicates with the high-pressure chamber. A mechanical ring that forms a shaft-sealing surface between the high-pressure chamber and the low-pressure chamber provided on the outer periphery of the rotary shaft, with a fixed ring provided with a communication hole and having its front end face biased toward the rear end face of the rotary ring. In the seal, a mechanical seal is characterized in that a corrugated groove is provided on the inner peripheral side of the shaft sealing surface of at least one of the rotary ring and the fixed ring.