JP6925101B2 - Shaft seal - Google Patents

Description

The present invention relates to a shaft seal.

Conventionally, as a shaft seal used in a vacuum pump, a resin seal element that is in sliding contact with a rotating shaft is held by being sandwiched between an outer case and an inner case (see, for example, Patent Document 1).
Further, as shown in FIG. 6, there is an outer case 91 and an inner case 92 in which the seal element 95 and the dust seal 96 for preventing the intrusion of dust from the atmosphere side X are held by sandwiching.

Japanese Unexamined Patent Publication No. 2007-22508

In recent years, shaft seals used in gas machines such as vacuum pumps and compressors are required to be applied to severe usage environments such as high speed (high sliding property) and dust resistance.
However, in the conventional shaft seal 9 as shown in FIG. 6, the dust seal 96 is bent in a free state toward the atmosphere side X in a J-shape in a vertical cross-sectional view to form a dust strip portion 96a, and the dust strip portion 96a is formed. Since the inner diameter dimension d9 of the inner peripheral edge 96d of 96a is set smaller than the outer diameter dimension D of the rotating shaft K, as shown in FIG. 7, during operation (when the rotating shaft K rotates), dust strips are set. High-temperature sliding heat generation is generated between the inner peripheral edge 96d of the portion 96a and the outer peripheral surface Ka of the rotating shaft K, and the dust strip portion 96
There is a problem that the physical properties of a change (decrease) and wear is promoted, and there is a problem that burn Kz is generated on the rotating shaft K and wear is further promoted.
Further, as shown in FIG. 8, since the dust seal 96 is pressed against the outer peripheral surface Ka by the elastic restoring force, the wear becomes faster and the burning becomes severe, the stable sealing performance cannot be exhibited, and the durability is also lowered. There was a problem such as (the life was shortened).

Therefore, an object of the present invention is to provide a shaft seal which can obtain excellent durability while exhibiting stable sealing performance for a long period of time.

The shaft seal according to the present invention is a shaft seal including a seal element that is in sliding contact with the rotating shaft and a dust seal for preventing dust from entering from the atmosphere side. The dust seal is the shaft of the rotating shaft. It has a flat shape orthogonal to the center and a straight shape with a uniform vertical cross-sectional wall thickness, and when assembled, the outer peripheral surface of the dust seal is in contact with the inner peripheral surface of the cylindrical wall of the outer case. The dust seal is positioned in the radial direction, the dust seal has a circular hole, and the inner diameter dimension of the circular hole in a free state is set to be smaller than the outer diameter dimension of the rotation shaft with a very small dimension, and the rotation Due to the initial wear that occurs when the rotation of the shaft is started, the inner diameter of the hole of the dust seal in the free state becomes the same as the outer diameter of the rotation shaft, and in the mounting operation state, the inner peripheral surface of the hole and the hole are described. The gap between the rotating shaft and the outer peripheral surface is zero, the sliding contact surface pressure is zero, and the inner peripheral surface of the dust seal is configured so as not to elastically press the outer peripheral surface of the rotating shaft.
Further, the wall thickness dimension of the dust seal is set to 0.3 times or more and 1.3 times or less the wall thickness dimension of the lip portion of the seal element.
Further, the seal element and the dust seal are made of PTFE.
Further, the inner peripheral surface of the dust seal is a smooth circumferential surface.

According to the present invention, the heat generated by sliding between the dust seal and the rotating shaft can be reduced, the life of the dust seal can be improved (life extension), and the sealing performance and durability can be significantly improved. The structure is simple and
Although it is easy to manufacture, it can prevent wear of the dust seal, prevent excessive heat generation during rotation, and can stably exhibit excellent sealing performance (dust resistance) for a long period of time. In particular, as a shaft seal for large machines used in a dusty atmosphere such as outdoors at a construction site or in a factory, the sealing performance against dust is improved, it can be sufficiently applied to high-speed rotation, and it has excellent durability.

It is a main part vertical sectional view which shows one Embodiment of the shaft seal of this invention. It is a vertical cross-sectional view of the main part which shows the mounting operation state. It is an enlarged vertical sectional view of a main part which shows an example of a dust seal in a free state. It is an enlarged cross-sectional view of a main part which shows another example of a dust seal in a free state. It is an enlarged vertical sectional view of the main part which shows the dust seal after the initial wear. It is a vertical sectional view of the main part which shows the conventional example. It is an enlarged vertical sectional view of a main part for demonstrating the problem of the conventional example. It is an enlarged vertical sectional view of a main part for demonstrating the problem of the conventional example.

Hereinafter, the present invention will be described in detail based on the illustrated embodiments.
As shown in FIGS. 1 and 2, the shaft seal according to the present invention includes a metal outer case 1 and a metal outer case 1.
It is provided with a metal inner case 2, a gasket 3 made of an elastic material such as rubber, and a resin seal element 6, and further, dust from the atmosphere side X is allowed to enter the atmosphere side X from the seal element 6. It is provided with a resin dust seal 7 to prevent it. (The dust seal 7 may be generally called a dust strip.)

The outer case 1 includes a cylindrical wall portion 11, an inner flange portion 12 extending radially inward from one end of the cylindrical wall portion 11 (the end of the atmosphere side X), and the other end of the cylindrical wall portion 11 (sealed). It has a small inner collar-shaped caulking bent piece 13 which is provided at the end of the chamber side Y and is bent in the radial inward direction in the assembly process. The outer case 1 does not have a small hole penetrating in the radial direction in the cylindrical wall portion 11.

The inner case 2 has an L-shaped vertical cross section and is fitted inwardly on the cylindrical wall portion 11 of the outer case 1. The inner flange portion 12 of the outer case 1 is formed by the caulked bent piece 13 of the outer case 1.
The gasket 3 works together with the cylindrical wall portion 21 pressed to the side and the inner flange portion 12 of the outer case 1.
It has an inner flange portion 22 that holds the seal element 6 and the dust seal 7 by sandwiching the seal element 6. The inner case 2 may have an I-shape or a square block shape.

The gasket 3 has an annular flat plate shape, and in the illustrated example, the inner flange portion of the inner case 2
Although it is interposed between the pressing surfaces of 22 and the seal element 6, it is interposed between the pressing surfaces of the seal element 6 and the dust seal 7 and between the pressing surfaces of the dust seal 7 and the inner flange portion 12 of the outer case 1. Is also good (not shown).

The seal element 6 has a uniform wall thickness, and in the free state of FIG. 1 (not attached between the housing H and the rotating shaft K), the vertical cross-sectional shape is J-shaped, and the outer An orthogonal plane wall portion 61 orthogonal to the axis L of the case 1 and a lip portion 62 capable of sliding contact with the outer peripheral surface Ka of the rotation axis K.
And a curved wall portion 63 that connects the two in a continuous manner.
As shown in FIG. 2, in the mounted operation state in which the seal element 6 is mounted between the housing H and the rotary shaft K and the rotary shaft K is rotating, the vertical cross-sectional shape of the seal element 6 is L-shaped, and the seal lip portion 62.
Has a cylindrical shape and is in sliding contact with the outer peripheral surface Ka of the rotating shaft K (hereinafter, may be referred to as a shaft outer peripheral surface Ka).

The dust seal 7 is for preventing dust such as dust and dirt from entering from the atmosphere side X to the back side (atmosphere side X) of the seal element 6, and the dust seal 7 is in a free state and a mounted state. In any case, it has an annular flat plate shape in the shape of an orthogonal plane of the axis, and a straight shape (single character shape) having a substantially uniform wall thickness in the vertical cross section.

The dust seal 7 has a circular hole 17, and is held at an angle between the inner flange portion 12 of the outer case 1 and the inner flange portion 22 of the inner case 2. Flat wall 71
And a dust strip portion 72 having an annular shape in the front view and a straight shape in the vertical cross section, which is provided so as to extend in the radial inward direction from the radial inner end portion of the axial center orthogonal plane wall portion 71, in a continuous manner (integrally). ) It can be said that it has. As shown in FIG. 2, the dust strip portion 72 is held in a plane orthogonal to the rotation axis K even in the mounted operation state.

The dust seal 7 and the seal element 6 are made of the same material and are made of PTFE (polytetrafluoroethylene).
Further, the dust seal 7 is made of one piece (one piece), and is easier to manufacture and has excellent dimensional accuracy as compared with the case where a plurality of pieces made of different materials are integrated by adhesion or the like.

The dust seal 7 is positioned in the radial direction by bringing its outer peripheral surface 7a into contact with the inner surface portion of the cylindrical wall portion 11 of the outer case 1 (directly).
The inner peripheral surface 7b of the hole 17 of the dust seal 7 is formed on a smooth circumferential surface. In other words, the labyrinth groove such as the inner peripheral concave groove and the spiral groove is omitted.

Then, as shown in FIGS. 1 and 3, in the unused (free) state, the inner diameter dimension d7 of the circular hole 17 of the dust seal 7 is set to be the same as the outer diameter dimension D of the rotating shaft K. Alternatively, as shown in FIG. 4, in the free state, the inner diameter dimension d7 of the dust seal 7 is set to be smaller than the outer diameter dimension D of the rotating shaft K with a very small dimension.
In the latter case, the dust seal 7 is slightly elastically deformed outward and inward in the state before the mounting operation in which the rotating shaft K is mounted between the housing H and the rotating shaft K and the rotating shaft K has not started to rotate. The peripheral surface 7b is lightly pressed against the outer peripheral surface Ka of the shaft.

Then, as shown in FIG. 5, when the rotation of the rotating shaft K is started, the gap between the inner peripheral surface 7b and the outer peripheral surface Ka of the shaft becomes zero due to initial wear (familiarity).
In other words, the inner diameter dimension d7 of the dust seal 7 is provided so as to have the same dimension as the outer diameter dimension D of the rotating shaft K due to the initial wear that occurs when the rotation of the rotating shaft K is started. That is, the above-mentioned extremely small dimensions are dimensions that can be worn by initial wear.

Further, in the mounted operation state, the dust seal 7 has an inner peripheral surface 7 after the initial wear is completed.
b does not elastically press the outer peripheral surface Ka of the shaft (even if the inner peripheral surface 7b and the outer peripheral surface Ka of the shaft are in contact with each other).
Wear that is greater than the initial wear does not occur, sliding heat generation is reduced (does not generate high-temperature sliding heat generation that changes physical properties), sealing performance is maintained, and sufficient durability is obtained.

On the other hand, in the former case, as shown in FIG. 3, the inner diameter dimension d7 of the dust seal 7 is set to be the same as the outer diameter dimension D of the rotating shaft K in the free state. The inner peripheral surface 7 of the hole 17 of the dust seal 7 in both the pre-operation state and the mounting operation state.
The gap between b and the outer peripheral surface Ka of the shaft becomes zero.

As described above, when the inner diameter dimension d7 of the hole 17 of the dust seal 7 is smaller than the outer diameter dimension D of the rotating shaft K in the free state as shown in FIG. 4, or as described above in FIG. In any case where it is the same as the outer diameter dimension D, in the mounted state, the same inner diameter dimension d7 as the outer diameter dimension D of the rotating shaft K is maintained, and the shape is a straight cross section --- an annular flat plate shape. When the rotating shaft K is rotating (during mounting operation), the gap between the inner peripheral surface 7b and the outer peripheral surface Ka of the shaft becomes zero.
In the conventional example shown in FIGS. 6 to 8, the elastic force that tries to elastically restore the bent dust strip portion 96a in the direction of arrow M is involved in the progress of wear of the inner peripheral edge 96d. In the present invention, the sliding contact surface pressure becomes zero and wear occurs from the beginning (in the case of FIG. 3) or after the initial wear (in the case of FIGS. 4 and 5). It hardly progresses and its lifespan is extended.

Further, as shown in FIG. 1, in the free state, the wall thickness dimension T7 of the dust seal 7 (dust strip portion 72) is 0.3 times or more and 1.3 times the wall thickness dimension T6 of the lip portion 62 of the seal element 6. It is set as follows. Preferably, it is set to 0.5 times or more and 1.1 times or less. If it is less than the lower limit value, there is a possibility that dust intrusion cannot be sufficiently prevented, and if it exceeds the upper limit value, the thickness dimension of the entire shaft seal becomes large and the material is wasted.

The grease (lubricant) may be held in the space S (see FIG. 2) between the dust seal 7 and the seal element 6.
Since the dust seal 7 is not deformed due to wear or the like for a long period of time, the grease is appropriately held for a long period of time.

As described above, the shaft seal of the present invention is a shaft seal including a seal element 6 that is in sliding contact with the rotating shaft K and a dust seal 7 for preventing dust from entering from the atmosphere side X. Maintains an annular flat plate shape having a circular hole 17 having the same inner diameter dimension d7 as the outer diameter dimension D of the rotating shaft K, and the gap between the inner peripheral surface 7b of the hole 17 and the outer peripheral surface Ka of the rotating shaft K is zero. Therefore, the sliding heat generation between the dust seal 7 and the rotating shaft K is reduced, local burn Kz (see FIG. 8) of the rotating shaft K is prevented, and the life of the dust seal 7 is extended. It can be improved (extended life) and the sealing performance and durability can be greatly improved. Although the structure is simple and easy to manufacture, it prevents the dust seal 7 from being worn, prevents excessive heat generation during rotation, and exhibits stable and excellent sealing properties (dust resistance) over a long period of time. can. In particular, as a shaft seal for large machines used in a dusty atmosphere such as outdoors at a construction site or in a factory, the sealing performance against dust is improved, it can be sufficiently applied to high-speed rotation, and it has excellent durability.

Further, since the wall thickness dimension T7 of the dust seal 7 is set to 0.3 times or more and 1.3 times or less of the wall thickness dimension T6 of the lip portion 62 of the seal element 6, the entire shaft seal can be formed thinly. Sufficient dust resistance (dust intrusion prevention performance) can be demonstrated. It can be easily manufactured and assembled.

Further, since the seal element 6 and the dust seal 7 are made of PTFE, sliding heat generation can be reduced and durability can be improved. The manufacturing process and material procurement of the seal element 6 can be shared with the dust seal 7 as they are, and the manufacturing cost can be reduced.

Further, since the outer peripheral surface 7a of the dust seal 7 is brought into contact with the cylindrical wall portion 11 of the outer case 1 to position the dust seal 7 in the radial direction, the dust seal 7 can be positioned in the radial direction with high accuracy, and the inside of the hole 17 can be positioned. The quality and performance can be stabilized by accurately setting the gap of the peripheral surface 7b with respect to the outer peripheral surface Ka of the shaft to zero.

Further, since the inner peripheral surface 7b of the dust seal 7 is a smooth circumferential surface, it is possible to reliably prevent the intrusion of dust while being easy to manufacture.

1 Outer case 6 Seal element 7 Dust seal 7a Outer peripheral surface 7b Inner peripheral surface
11 Cylindrical wall
17 holes
62 Lip part D Outer diameter dimension d7 Inner diameter dimension K Rotating axis Ka Outer peripheral surface
L Axis T6 Wall Thickness Dimension T7 Wall Thickness Dimension X Atmospheric Side

Claims (4)

In a shaft seal provided with a seal element (6) that is in sliding contact with the rotating shaft (K) and a dust seal (7) for preventing dust from entering from the atmosphere side (X).
The dust seal (7) has a planar shape orthogonal to the axis (L) of the rotation axis (K), and has a straight shape having a uniform vertical cross-sectional wall thickness.
In the assembled state, the outer peripheral surface (7a) of the dust seal (7) is attached to the outer case (1).
), The dust seal (7) is positioned in the radial direction so as to be in contact with the inner peripheral surface of the cylindrical wall portion (11).
The dust seal (7) has a circular hole (17), and the inner diameter dimension (d7) of the circular hole (17) in the free state is extremely smaller than the outer diameter dimension (D) of the rotating shaft (K). The inner diameter dimension (d7) of the hole (17) of the dust seal (7) in the free state is set to be smaller with a smaller dimension due to the initial wear caused by the start of rotation of the rotating shaft (K). )
The gap between the inner peripheral surface (7b) of the hole (17) and the outer peripheral surface (Ka) of the rotating shaft (K) is zero in the mounting operation state, which is the same as the outer diameter dimension (D) of. Further, the shaft seal is characterized in that the sliding contact surface pressure becomes zero and the inner peripheral surface (7b) of the dust seal (7) does not elastically press the outer peripheral surface (Ka) of the rotating shaft (K). Claim 1 in which the wall thickness dimension (T7) of the dust seal (7) is set to 0.3 times or more and 1.3 times or less the wall thickness dimension (T6) of the lip portion (62) of the seal element (6). Described shaft seal. The shaft seal according to claim 1 or 2, wherein the seal element (6) and the dust seal (7) are made of PTFE. The shaft seal according to claim 1, 2, or 3, wherein the inner peripheral surface (7b) of the dust seal (7) is a smooth circumferential surface.

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