JP4763480B2 - Rotating shaft seal - Google Patents

Description

  The present invention relates to a rotary shaft seal having a seal element.

  Conventionally, a rotary shaft seal as shown in FIG. 4 is used in a dry vacuum pump or the like. In recent years, there has been a demand for vacuum pumps with high discharge performance in the semiconductor industry as the efficiency increases, and in the liquid crystal industry as the size of manufacturing equipment increases, and rotary shaft seals used in such vacuum pumps. Is in a severe environment of high rotation, wear is significant, and durability is a problem.

Such a conventional rotary shaft seal has a structure in which a seal element 31 is held in a sandwiched manner by an inner case 32 and an outer case 33, as illustrated in the enlarged cross-sectional view of the main part of FIG. A fixed portion 31a on the outer peripheral side of the thin flat plate annular seal element 31 is sandwiched between the inner flange portion 33a of the outer case 33 and the inner flange portion 32a of the inner case 32 with an elastic gasket 34 interposed therebetween. It is stuck. 35 is a caulking bent piece for assembling the inner case 32, the seal element 31, and the gasket 34 in this manner, and is formed on the high pressure side A of the outer case 33 having a substantially L-shaped cross section. Is done.
The seal element 31 has a substantially J-shaped or substantially L-shaped cross section in the mounted and used state. FIGS. 5A and 5B show the oil temperature 25 in the mounted and used state using FEM analysis. Draw the contact surface pressure distribution and its position by analyzing the shape of the seal element 31 under the conditions of ℃ and oil pressure of 60 KPa, oil temperature of 200 ℃ and oil pressure of 60 KPa, and the contact surface pressure against the outer peripheral surface of the rotating shaft S It is a figure.

As shown in FIG. 5 (a), when the seal element 31 is mounted on the rotary shaft S, the dotted flat plate-shaped ring is bent into a substantially J shape, and under the use conditions of 25 ° C. and 60 KPa described above, Only the leading edge 36a of the slidable contact wall 36 contacts the rotating shaft S in a line contact manner.
The peak 40 of the contact surface pressure P is generated at the forefront edge 36a, and a portion Z surrounded by a thick alternate long and short dash line is a wear generation portion. Thus, as shown in FIG. 5A, when the oil temperature is as low as 25 ° C., the peak 40 is generated and the oil is completely sealed at the leading edge 36a that is in sliding contact with the line. In addition, since the wear generation site Z is generated from the leading edge 36a, the peak 40 of the contact surface pressure P is always generated at the position 36a, and the sealing performance can be maintained.

Even if the pressure in the sealed chamber 37 rises, the contact pressure resistance is maintained by the pressure and the tightening pressure of the seal element.
However, in recent vacuum pumps and the like (as described above), the rotation speed is gradually increased, and the sliding contact wall portion 36 of the seal element 31 generates heat due to frictional heat with the rotation shaft S, and the seal element made of a material such as PTFE is used. For example, at 200 ° C., the strength of 31 is significantly reduced, and as shown in FIG. 5B, the cross-section is deformed to a substantially L-shaped shape. In addition, the peak 40 is generated, and the contact surface pressure distribution is also enlarged (in the axial direction) to form a surface contact, which easily causes external leakage. In addition, the wear occurrence site Z also moves to the low pressure side B from the leading edge 36a, and only this wear occurrence site Z wears in a concave shape, and wears the seal element 31 from the back of the concave wear groove. To cause leakage.

In order to solve such a problem, there has conventionally been provided a structure in which a large number of wavy small irregularities are formed on the outer surface of the curved wall portion of the seal element (see, for example, Patent Document 1).
JP 2002-013643 A

  However, in the sealing element in which a large number of the wavy small undulations described above are arranged, it is bent into a substantially L shape approximate to FIG. There was also a problem of concentration and cracking.

  Therefore, the present invention prevents cracks due to such stress concentration, and skillfully moves the position of occurrence of the peak of the contact surface pressure to the outer peripheral surface of the rotating shaft of the seal element to the most advanced edge, causing wear, It is an object of the present invention to provide a rotary shaft seal that can exhibit excellent sealing performance for a long period of time and can cope with high-speed rotation with excellent durability.

Therefore, the rotary shaft seal according to the present invention includes a seal element having a cross-sectional shape bent into a substantially J-shaped or substantially L-shaped cross section via a curved wall portion , and the seal element includes the curved wall portion and the curved wall portion. over cutting edge portion from the curved wall portion, in addition to the rotation axis at a rotation shaft seal to keep the non-contact state with respect to the other member, to form a shallow band of the groove portion on the outer side of the curved wall portion of the seal element Te, the entire or most part of the curved wall portion and a thin portion, further, the corner portion of the recessed groove portion, formed in a rounded shape to avoid stress concentration, the rotating the forefront edge with the peak of contact pressure and configured to come in contact with the normal to the line contact with the outer peripheral surface of the shaft.

According to the present invention, stress concentration does not occur in the curved wall portion of the seal element, it is possible to prevent cracks, cuts, etc., and the leading edge of the seal element always contacts, It exhibits stable sealing performance, excellent durability, in particular, exhibits excellent sealing performance and durability that can also be correspond to high-speed rotation such as a vacuum pump.

Hereinafter, the present invention will be described in detail based on the illustrated embodiment.
FIG. 1 is an enlarged sectional perspective view of an essential part showing an embodiment of the present invention, FIG. 2 is an enlarged sectional view of an essential part, and FIG. 3 is an FEM analysis diagram for explaining the operation and effect of the present invention. In FIG. 1 to FIG. 3, reference numeral 1 denotes a seal element, which is made of a material such as PTFE and is held in a sandwiched (crushing pressure) shape by a metal inner case 2 and an outer case 3. The fixing portion 1a on the outer peripheral side of the thin flat plate annular seal element 1 is formed by the inner flange portion 3a of the outer case 3 and the inner flange portion 2a of the inner case 2 with the gasket 4 of an elastic material such as rubber interposed. It is firmly attached in a pinched form. 5 is a caulking bent piece, and in the state indicated by a two-dot chain line in FIG. 2, the gasket 4, the seal element 1, and the inner case 2 are sequentially inserted into the outer case 3, and the arrow M direction It is crimped and assembled in a single piece under pressure.

The outer case 3 has a substantially L-shaped cross-section, and a cylindrical wall portion 3b to be fitted by applying a liquid gasket to the inner peripheral surface of a hole portion (not shown) of a casing of a vacuum pump (not shown), and an axial center It consists of an inner flange portion 3a in the orthogonal direction and a small inner flange-shaped crimping piece 5, which corresponds to the high pressure side (sealed fluid chamber side) A that seals the fluid, The part 3a corresponds to the low pressure side such as the atmosphere.
The inner case 2 has an L-shaped cross section, and includes a cylindrical wall portion 2b fitted to the inner peripheral surface of the cylindrical wall portion 3b of the outer case 3, and an inner flange portion 2a in the direction orthogonal to the axis.

The seal element 1 is formed of an annular flat plate-like PTFE material or the like, and has a cross-sectional shape that is bent into a substantially J-shaped or substantially L-shaped cross section via a curved wall portion 6 in a mounted state. .
A shallow belt-like concave groove portion 7 is formed in the curved wall portion 6 of the seal element 1. 1 to 3 exemplify a case where one shallow groove-like concave groove portion 7 is provided outside the curved wall portion 6 .
In this way, the whole or most of the curved wall portion 6 is formed in the thin portion Y.

FIG. 3 shows the shape of the PTFE seal element 1 and the contact surface pressure P with respect to the outer peripheral surface of the rotating shaft S under the conditions of an oil temperature of 200 ° C. and an oil pressure of 60 KPa. It is the graph analyzed by analysis, the horizontal axis of FIG. 3 shows an axial center position, and the dotted line 8 shows a non-wearing state.
As can be seen from FIG. 3, in the present invention, compared to FIG. 5 (b) showing an example of the oil temperature of 200 ° C. and the oil pressure of 60 KPa, the present invention is substantially J-shaped rather than substantially L-shaped. And the leading edge 10 on the high pressure side A always contacts the outer peripheral surface of the rotating shaft S as a line contact with the peak 40 of the contact surface pressure P.

Then, as shown in FIG. 3 (b), the depth of the concave groove 7 and H _7, if the width and W _7, it is desirable in the present invention are set as follows. In addition, let T be the average thickness dimension of parts other than the thin part Y. That is,
0.10 × T ≦ H ₇ ≦ 0.30 × T
1.0 × T ≦ W ₇ ≦ 3.0 × T
The depth dimension H ₇ and the width dimension W ₇ are set as follows . Also, the corner portion 12, 12 of the recessed groove portion 7 avoid stress concentration formed in a round shape.

  As described above, the present invention relates to a rotary shaft seal provided with a seal element 1 having a cross-sectional shape that is bent in a substantially J-shaped or substantially L-shaped cross-section via a curved wall portion 6. Therefore, the amount of frictional heat generated when the seal element 1 is slidably contacted with the rotating shaft S during high-speed rotation increases, and the seal element 1 becomes high temperature. Although the material strength is reduced, the curved wall 6 is thinner than its tip, so that a peak 40 of the contact surface pressure P always occurs at the leading edge 10, and this causes wear to occur. Occurs at the edge 10 and exhibits a stable sealing property over a long period of use (no corrugated wear recesses occur in the middle).

  Further, in the rotary shaft seal provided with the seal element 1 having a cross-sectional shape bent in a substantially J-shaped or substantially L-shaped cross-section via the bent wall portion 6, the bent wall portion 6 of the seal element 1 is shallow. Since the belt-shaped concave groove portion 7 is formed and the leading edge 10 is always in line contact with the outer peripheral surface of the rotating shaft S with the peak 40 of the contact surface pressure when mounted and used, No wear-out recesses are generated, and a stable sealing performance is exhibited over a long period of use. Furthermore, since it contacts the outer peripheral surface of the rotating shaft S as a line contact, it is possible to effectively prevent external leakage associated with the oil film and to exhibit even better sealing performance. Particularly, it is suitable for sealing a vacuum pump, and can sufficiently cope with high speed. Further, since the concave groove portion 7 has a shallow belt shape, stress concentration does not occur in the seal element 1, cracks and breakage can be prevented, and a long-life seal can be obtained. In short, even under the severe conditions of high-speed rotation, it stably exhibits excellent sealing properties (sealing performance) and has excellent durability.

It is a principal part expanded sectional perspective view which shows one Embodiment of this invention. It is a principal part expanded sectional view. It is a FEM analysis graph figure for description of the effect of this invention. It is a principal part expanded sectional view which shows a prior art example. It is a FEM analysis graph figure for demonstrating the problem of a prior art example.

1 Seal Element 6 Curved Wall 7 Groove
10 Cutting edge
12 corners
40 Peak S Rotating shaft P Contact surface pressure
Y thin part

Claims (1)

A seal element (1) having a cross-sectional shape bent into a substantially J-shaped or substantially L-shaped cross section via a bent wall portion (6) , and the seal element (1) includes the bent wall portion (6) and In the rotary shaft seal that keeps a non-contact state with respect to other members other than the rotary shaft (S) from the curved wall portion (6) to the leading edge (10) ,
A shallow belt-shaped concave groove (7) is formed outside the curved wall portion (6) of the sealing element (1), and the whole or most of the curved wall portion (6) is a thin-walled portion (Y).
Furthermore, the corners (12) and (12) of the concave groove (7) are formed in a round shape to avoid stress concentration,
A rotary shaft seal characterized in that the foremost edge (10) is always in line contact with the outer peripheral surface of the rotary shaft (S) with a peak (40) of contact surface pressure (P) .

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