JPH04337164A - Non-contact type seal device - Google Patents

Abstract

PURPOSE:To enable the use of a non-contact seal device in a high speed and high pressure operation condition, to keep parallelism between seal surfaces without being influenced by the strain of a seal surface owing to pressure and heat, and to reduce an amount of leakage caused by a difference of pressure between seals. CONSTITUTION:Spiral grooves 19 for generating dynamic pressure are formed at equal intervals in the peripheral direction throughout the whole periphery of a seal surface 5a. Reversing groove parts 20 extending in the reverse direciton in the peripheral direciton and having a closed inner end are formed in a communicating state in the inner end of the spiral groove.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is used for shaft seals of rotary air machines such as turbines, blowers, and compressors. This invention relates to a non-contact type sealing device.

0002

[Prior Art] Generally, in this type of device, an end face perpendicular to the axis of a rotary seal ring that rotates with a rotating shaft passing through a casing, and an end face opposite to the end face of a stationary ring held on the casing side. is used as a non-contact sealing surface between the two.

As shown in FIG. 8, one of the conventional typical structures for keeping the seal surfaces in a non-contact state is a spiral-shaped seal surface 81a of a rotary seal ring 81 for generating dynamic pressure from the outer circumferential side to the inner circumferential side. grooves 82 are formed at equal intervals in the circumferential direction around the entire circumference,
As the rotary seal ring 81 rotates, pressure fluid is forcibly drawn between the seal surfaces due to the pumping action of its spiral groove 82, causing the seal surfaces to float.

However, in such a configuration, it is difficult to maintain the sealing surfaces in a stable parallel state in gas turbines and compressors that operate at high speed and high pressure, making it difficult to achieve good sealing performance. It's hard to let it happen. For this reason, as disclosed in Japanese Patent Publication No. 1-22509, etc., a device has been proposed in which the sealing surfaces of the rotating seal ring and the stationary ring are provided with a self-aligning function. This seal is designed to prevent distortion of the seal surface by appropriately setting three parameters: the depth of the spiral groove, the ratio of the radial width to the seal surface, and the balance ratio. A moment is automatically created to maintain the parallelism of the sealing surfaces.

[0005]

[Problem to be solved by the invention] In conventional non-contact sealing devices that do not have a self-aligning function, when distortion occurs in the sealing surface due to the influence of pressure strain or thermal strain, the sealing surface becomes distorted due to the narrow gap between the sealing surfaces. partial contact occurs. As a result, the pressure balance of the seal collapses, heat generation increases, and seal surface distortion is further promoted, eventually leading to seal failure. Even in the seal with the self-alignment function shown in the above-mentioned Japanese Patent Publication No. 1-22509, which improves on this problem, due to restrictions on parameter settings, the seal surfaces come into contact when stopped, and leakage is promoted during rotation. There is a problem that directional dynamic pressure is generated and the amount of leakage increases.

The present invention has been developed in view of the above-mentioned circumstances, and is applicable to high-speed, high-pressure operation, suppresses loss of pressure balance due to distortion due to fluid pressure and heat, and prevents leakage from the sealing surface. It is an object of the present invention to provide a non-contact type sealing device that can be made smaller and eliminate the risk of damage to the sealing surface.

[0007]

[Means for Solving the Problem] In order to achieve the above object, the non-contact type sealing device according to the invention of claim 1 is provided with spiral grooves for generating dynamic pressure in the sealing surface evenly circumferentially around the entire circumference. In the case where the spiral groove is formed at intervals, an inverted groove portion with an inner end closed and extending in opposite directions in the circumferential direction is formed in a communicating state at the inner end of the spiral groove.

In particular, the ratio of the overall radial width of the spiral groove and inverted groove for generating dynamic pressure to the radial width of the sealing surface is set to 0.5 to 0.7. It is preferable to do so.

Furthermore, the ratio of the radial width of the spiral groove for generating dynamic pressure to the radial width of the entire spiral groove and inverted groove is set to 0.6 to 0.6.
It is more preferable to set it to 0.7.

0010

[Operation] According to the invention of claim 1 having the above structure, the high pressure fluid is taken in by the spiral groove for generating dynamic pressure formed in the sealing surface, and the parallel state between the sealing surfaces is stably maintained. In addition to making it easier to use under high-speed and high-pressure conditions, if the sealing surfaces tend to tilt due to strain due to pressure or heat, the pumping action of the reversing grooves generates a moment that returns them to parallel planes, preventing the sealing surfaces from coming into contact with each other. In addition, the amount of leakage due to the pressure difference is suppressed to a small level, and since the inner end of the reversing groove is closed, there is no fear of dust or the like entering.

Furthermore, according to the second aspect of the present invention, collapse of the pressure distribution due to pressure strain or thermal strain on the sealing surface is reliably suppressed.

Furthermore, according to claim 3, it is possible to effectively generate an average dynamic pressure over the entire sealing surface.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an enlarged longitudinal cross-sectional view of essential parts showing an example of a non-contact type sealing device according to the present invention. In the same figure,
1 is a casing, 2 is a rotating shaft passing through the casing 1,
3 is a fixing ring fixed to the inner wall of the casing 1. A stationary ring 4 is held on the side of the stationary ring 3 and has an end surface 4a perpendicular to the axis. Reference numeral 5 denotes a rotary seal ring that is attached to the outer peripheral side of the rotary shaft 2 and rotates together with the rotary shaft 2, and the end face 4a of the stationary ring 4
It has an end surface 5a facing to. These both end surfaces 4a, 5a
The sealing surface is constituted by:

The fixing ring 3 is axially positioned by a stopper member 6 and the like, and an O-ring 7 prevents leakage between the fixing ring 3 and the casing 1. A plurality of blind holes 8 are formed in a surface perpendicular to the axis of the fixing ring 3 at equal intervals in the circumferential direction. A spring member 9 is seated in each of these blind holes 8, and these spring members 9 are connected to the stationary ring 4 through a disk 10 having an L-shaped cross section that is overlapped and fixed to the stationary ring 4.
A spring force is applied in the axial direction. The space between the fixing ring 3 and the disk 10 is sealed by an O-ring 11.

Reference numeral 12 denotes a first sleeve fitted to the rotating shaft 2, and 13 a second sleeve fitted to the first sleeve 12, which is connected to the flange portion 12a of the first sleeve 12. The rotary seal ring 5 is positioned in the axial direction by the second sleeve 13. 14 is an O-ring for preventing leakage between the first sleeve 12 and the rotary shaft 2; 15 and 16 are O-rings for preventing leakage between the rotary seal ring 5 and the first sleeve 12;
It's a ring. Reference numeral 17 indicates a pin for stopping rotation of the rotary seal ring 5 with respect to the rotation shaft 2, and reference numeral 18 indicates an auxiliary labyrinth seal.

Among the seal surfaces 4a and 5a of the stationary ring 4 and the rotating seal ring 5, one seal surface 5a
As shown in FIG. 2, a plurality of spiral grooves 19 for generating dynamic pressure are formed from the outer circumferential side to the inner circumferential side. The depth of this spiral groove 19 for generating dynamic pressure is 2 to 2.
It is preferable to set the thickness to 10 μm. At the inner end of this spiral groove 19 for generating dynamic pressure, as shown in FIG. 2, a tapered inversion groove portion 20 extending in opposite directions in the circumferential direction and closed at the inner end is formed in a communicating state.

In such a configuration, when the rotary shaft 2 rotates, the rotary seal ring 5 rotates accordingly. A spiral groove 19 for generating dynamic pressure is formed in the sealing surface 5a of the rotary seal ring 5, so that the pumping action of the groove 19 forces fluid to flow between the sealing surfaces 4a and 5a. be done. As a result, both seal surfaces 4
A membrane with a constant sealing fluid pressure (FIG. 3) is ensured between a and 5a, allowing desired leakage due to the minute gap.

Even when fluid pressure fluctuates, the pressures applied to both end surfaces of the stationary ring 4 and the disk 10 are always balanced, allowing stable operation.

In particular, even if the seal surfaces 4a, 5a are distorted due to fluid pressure or heat generated during high-speed operation and the pressure balance is about to collapse, the inside end of the spiral groove 19 for generating dynamic pressure is The tip 20 of the reversal groove 20 that communicates with
A moment around the center of rotation is obtained by the maximum pressure generated near a, and the seal surfaces 4a and 5a can always be kept in parallel planes.Moreover, the amount of leakage is reduced by the pumping action in the direction of pushing back the leakage at the seal surfaces 4a and 5a. can be made smaller.

By the way, the pressure distribution when the sealing surfaces 4a, 5a are not strained by pressure or heat is as shown in FIG. It depends on the radial forming width dimensions b1 and b2 (FIG. 3) for the sealing surface 5a of 20.

Now, the radial width dimension of the sealing surface 5a is b
, b1 is the overall radial width of the dynamic pressure generating groove 19 and the reversing groove 20, and b2 is the radial width of the dynamic pressure generating groove 19, then b1/b=0.5 to 0. It is preferable to set it within the range of .7.

When b1/b<0.5, the pressure generated in the dynamic pressure generating groove 19 and the reversing groove 20 is weak;
Even if pressure is generated, it will be limited to a narrow area on the outer peripheral side of the seal surfaces 4a, 5a, and the pressure will not be large enough to prevent the seal surfaces 4a, 5a from coming into contact with each other.

In addition, in the case of b1/b>0.7, when the external height distortion as shown in FIG. 5 occurs, the pressure distribution becomes P1<Q, and the gap between the seal surfaces 4a and 5a becomes smaller. There is a possibility that the seal surfaces 4a and 5a will come into contact with each other. On the contrary, Figure 6
When an internal high strain as shown in FIG. 2 occurs, the pressure distribution becomes P2>Q, so the gap between the seal surfaces 4a and 5a is widened, and eventually P3=Q, so there is no problem.

Therefore, by setting b1/b=0.5 to 0.7, when the external height is strained, the pressure distribution becomes such that the pressure P4>Q as shown in FIG. 7, and the seal surfaces 4a, 5a The gap widens, and in the case of internal high strain, the pressure distribution becomes P5=Q. In other words, the pressure distribution on the seal surfaces 4a, 5a is balanced regardless of the internal height strain or the external height strain, and the risk of contact between the seal surfaces 4a, 5a can be reliably eliminated.

[0026] Regarding b2/b1, 0.6 to 0
．． It is preferable to set it to 7. The reason is as follows. That is, when b2/b1<0.6, the dynamic pressure generating effect in the dynamic pressure generating groove 19 is insufficient, and it is difficult to obtain enough pressure to bring the seal surfaces 4a and 5a out of contact with each other. In addition, in the case of b2/b1>0.7, when external height distortion occurs, the gap between the seal surfaces 4a and 5a becomes smaller due to collapse of the pressure balance, and there is a possibility that the seal surfaces 4a and 5a come into contact with each other.

Furthermore, since the inner end of the reversing groove portion 20 is closed, dust from the atmosphere and oil mist from the bearings are not drawn into the sealing surface 5a, so that the sealing surfaces 4a and 5a are protected by them. There's no risk of getting hurt.

In the above embodiment, the spiral groove 19 for generating dynamic pressure and the reversing groove 20 were formed on the sealing surface 5a of the rotating seal ring 5. However, these grooves 19, 20, etc. Even if it is provided on the fourth side, the same effect can be achieved.

Further, the shape of the reversing portion 20 is not limited to the tapered shape as described above, and may be arbitrarily selected and set.

[0030]

As described above, according to the present invention, at the inner end of the spiral groove for generating dynamic pressure formed on the sealing surface,
Since the inverted grooves with closed inner ends extending in opposite directions in the circumferential direction are formed in a communicating state, it is possible to stabilize the sealing surface during high-speed and high-pressure operation, and to reduce the amount of leakage due to the pressure difference between the sealing surfaces.
This can be reduced by the pumping action in the push-back direction by the above-mentioned reversing groove, and also improves reliability by correcting the inclination of the sealing surface due to pressure strain, thermal strain, etc., eliminating performance degradation caused by sealing surfaces coming into contact with each other. can be increased.

Further, according to the second aspect of the present invention, it is possible to obtain a pressure distribution without fear of contact between the seal surfaces even when external height distortion occurs on the seal surfaces.

Furthermore, according to claim 3, it is possible to reliably obtain an average dynamic pressure over the entire sealing surface.

[Brief explanation of drawings]

FIG. 1 is an enlarged vertical cross-sectional view of essential parts of a non-contact sealing device according to an embodiment of the present invention.

FIG. 2 is a front view showing the sealing surface of the rotary seal ring.

FIG. 3 is a diagram showing the radial dimensional relationship of a dynamic pressure generation groove and a reversal groove portion.

FIG. 4 is a diagram showing the pressure distribution on the sealing surface when no distortion occurs.

FIG. 5 is a diagram showing the pressure distribution on the sealing surface when external height distortion occurs.

FIG. 6 is a diagram showing the pressure distribution on the sealing surface when internal high strain occurs.

FIG. 7 is a diagram showing the pressure distribution on the sealing surface when the overall radial width dimensions of the dynamic pressure generation groove and the reversal groove are set.

FIG. 8 is a diagram showing a sealing surface of a conventional non-contact type sealing device.

[Explanation of symbols]

1 Casing 2 Rotation axis 4 Stationary ring 4a, 5a Seal surface 5 Rotating seal ring 19 Spiral groove for generating dynamic pressure 20 Inversion groove part

Claims (3)

[Claims] 1. An end face perpendicular to the axis of a rotating seal ring that rotates with a rotating shaft passing through a casing, and an end face opposite to the end face of a stationary ring held on the casing side are both seal surfaces, In a non-contact type sealing device, spiral grooves for generating dynamic pressure, which take in high-pressure fluid from the outer circumferential side to the inner circumferential side, are formed at equal intervals circumferentially around the entire circumference on either one of the sealing surfaces, A non-contact type sealing device characterized in that an inverted groove portion with an inner end closed and extending in opposite directions in the circumferential direction is formed at the inner end of the spiral groove in a communicating state. 2. The ratio of the overall radial width of the dynamic pressure generating spiral groove and the reversal groove to the radial width of the sealing surface is set to 0.5 to 0.7. The non-contact type sealing device according to claim 1, characterized in that. 3. The ratio of the radial width of the spiral groove for generating dynamic pressure to the radial width of the entire spiral groove and inverted groove is 0.6 to 0.7.
2. The non-contact type sealing device according to claim 1, wherein the non-contact type sealing device is set as follows.