JP2001173798A - Oil seal with screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oil seal with a screw having a simple structure and being capable of retaining stable sealing performance for a long time from an initial stage of using the oil seal. SOLUTION: In this oil seal with the screw where multiple helical screws connected to a lip tip 8 projects on a sealing surface 10, the screw is composed of a specified height screw 15 with a specified height in the longitudinal direction and a shoulder screw 16 comprising a low protrusion part 16a with approximately the same height at a part near the lip tip to the specified height screw and a high protrusion part 16c with a height higher than that of the low protrusion part 16a at a part distant from the lip tip.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a threaded oil seal which is a kind of a sealing device used for preventing leakage of a sealed fluid.

[0002]

2. Description of the Related Art In general, a portion such as a crankshaft or a camshaft of an engine mounted on an automobile is exposed to the outside, and is made of a rubber-like elastic body or the like for preventing leakage of lubricating oil as a sealing fluid. Annular oil seals are frequently used. As one type of oil seal, a threaded oil seal in which a plurality of helical screws for hydrodynamically supporting a sealing function on a sealing surface is known.

Hereinafter, such a conventional oil seal with a screw will be described with reference to FIGS.

As shown in FIG. 7, a conventional oil seal 1 with a screw is formed so as to be mounted between a rotating shaft (crankshaft) 2 and a housing 3. And
The threaded oil seal 1 is formed by integrally baking a seal main body 5 formed of a rubber-like elastic body on an annular reinforcing ring 4 having a substantially L-shaped cross section.

[0005] The seal body 5 has a sealing side O on which a sealing fluid such as lubricating oil (not shown) is located from the inner peripheral portion of the reinforcing ring 4.
An annular seal lip 6 formed to gradually decrease in diameter toward S, and an annular dust lip 7 formed to gradually reduce in diameter from the inner peripheral portion of the reinforcing ring 4 to the atmosphere side AS. The seal lip 6 has a suitable interference with the rotating shaft 2, and has a lip tip 8 that comes into contact with the rotating shaft 2. The seal lip 6 has an oil surface 9 having a predetermined oil surface angle which is enlarged from the lip tip 8 toward the sealing side OS and a predetermined oil surface 9 which is enlarged from the lip tip 8 to the atmosphere side AS. A seal surface 10 having a seal angle, and a desired region of the seal surface 10 on the lip tip 8 side is brought into contact with the surface of the rotating shaft 2 with an appropriate interference in the mounted state. A garter spring 11 for holding a radial tension between the seal lip 6 and the rotary shaft 2 is disposed on a radially outer rear surface of the lip tip 8 of the seal lip 6.

Further, a sealing fluid such as lubricating oil (not shown) that is leaking from the sealing side OS toward the atmosphere side AS is always positioned on the sealing side OS on the sealing surface 10 which is in contact with the rotating shaft 2 in the mounted state. A plurality of screws 12 having a pumping action to protrude are provided. This screw is
As shown in FIG. 10, the inclination angle θ1 is 20 to 3
About 0 degree, vertex angle θ2 is about 80-100 degrees, sealing surface 1
The height H from 0 to the apex is approximately triangular in cross section with a height of about 0.03 to 0.08 mm, and the tip 13 of the screw 12 located on the lip tip 8 side is connected to the lip tip 8. .

[0007] The lip tip 8 is formed by finishing using an oil seal scalpel (not shown).

[0008]

However, in the above-mentioned conventional oil-sealed thread seal 1, as the operating time (rotation time of the rotating shaft 2) increases, the lip tip 8 is increased.
Of the screw 12 which is in contact with the rotating shaft 2 together with the lip tip 8 on the side of the lip tip 8 due to increased wear of the
As the wear of the lip tip 8 increases, the sealing performance gradually decreases, and the life of the lip end 8 increases until the leakage occurs. There was a problem that it was short.

To solve this problem, Japanese Patent Laid-Open No.
In Japanese Patent No. -19135, as shown in FIG. 11, the height of the screw 12a in the area near the lip tip 8 is set to a low protruding portion having almost the same height as that of the conventional example, and in the area away from the lip tip 8 An oil seal has been proposed in which the height of the screw 12a is formed as a high protuberance that is about five times as high as the height of the low protuberance. By forming the screw 12a into a stepped shape having two heights in the longitudinal direction, as the low ridge of the screw 12a having a low height wears as the lip tip 8 wears, the height of the screw 12a increases. Since the tall high ridge gradually comes into contact with the mating member, it is possible to prevent a decrease in sealing performance.

[0010] However, the oil seal described in the above publication has a high protruding portion in which the height of the screw 12a is high, so that the pitch of all the screws 12a must be formed large. There is a limit to the number of screws that can be placed on the lip tip 8 and, consequently, the amount of pumping at the initial stage of wear of the lip tip 8.

Therefore, the pumping amount of the oil seal lip tip 8 in the initial stage of wear is sufficiently maintained, and even if the wear of the lip tip 8 increases as the operating time increases, the pump action by the screw 12a is reduced. It has been desired to reduce the pressure and maintain stable sealing performance over a long period of time.

The present invention has been made in view of the above points, and provides a threaded oil seal having a simple structure and capable of maintaining stable sealing performance for a long period of time from the initial use of the oil seal. The purpose is to:

[0013]

According to the first aspect of the present invention, there is provided a threaded oil seal according to the first aspect of the present invention.
In a threaded oil seal formed by projecting a plurality of helical screws connected to a lip tip on a sealing surface, the screw has a constant height screw whose height is constant in a longitudinal direction, and a lip tip of the screw. A stepped screw having a low protuberance having a height near the same height as the constant height screw and a high protuberance whose height remote from the lip tip is higher than the low protuberance. It is characterized by having. With this configuration, in the early stage of use when the unworn lip tip comes into contact with the counterpart, the constant height screw and the low protruding part of the stepped screw contact the counterpart, and a sufficient pump amount can be obtained. As the tip wear progresses, the high ridge of the stepped screw gradually comes into contact with the counterpart, so that a reduction in the pump amount can be reduced. As a result, stable sealing performance can be maintained for a long period of time from the initial use of the oil seal.

According to a second aspect of the present invention, there is provided a threaded oil seal according to the first aspect, wherein the constant high thread and the stepped thread are alternately arranged in a circumferential direction. It is characterized by being. With this configuration, the constant height screw and the stepped screw are evenly arranged in the circumferential direction, so that the pump amount is also equal in the circumferential direction, and high-precision sealing performance can be exhibited.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments shown in the drawings. The same or corresponding components as those of the above-described conventional device are denoted by the same reference numerals in the drawings.

FIGS. 1 to 6 show a first embodiment of a threaded oil seal according to the present invention. As shown in FIG. 1, the threaded oil seal 14 of the present embodiment is formed so as to be mounted between the rotating shaft 2 and the housing 3. The threaded oil seal 14 is formed by integrally baking a seal main body 5 formed of a rubber-like elastic body on an annular reinforcing ring 4 having a substantially L-shaped cross section.

The seal body 5 has an annular seal lip 6 formed so as to gradually decrease in diameter from the inner periphery of the reinforcing ring 4 toward the sealing side OS. An annular dust lip 7 is formed so as to gradually decrease in diameter toward the side AS, and the seal lip 6 has an appropriate interference with the rotating shaft 2 and comes into contact with the rotating shaft 2. It has a lip tip 8. And seal lip 6
The oil surface 9 has a predetermined oil surface angle which is enlarged from the lip tip 8 toward the sealing side OS, and the seal has a predetermined seal angle which is enlarged from the lip tip 8 to the atmosphere side AS. Lip tip 8 of the sealing surface 10
A desired area on the side is brought into contact with the surface of the rotating shaft 2 with an appropriate interference in the mounted state. Also,
A garter spring 11 for maintaining a radial tension between the seal lip 6 and the rotary shaft 2 is disposed on a radially outer rear surface of the lip tip 8 of the seal lip 6.

The sealing surface 10 is provided with two kinds of screws 15 having a pumping function for always positioning a sealing fluid such as a lubricating oil (not shown) which is to leak from the sealing side OS toward the atmosphere side AS on the sealing side OS. , 16 are alternately and equally formed in the circumferential direction. These screws 15 and 16 have an inclination angle θ1 of 15 to 3 as shown in detail in FIGS.
0 degrees, about 20 degrees in the present embodiment, and the apex angle θ2 is 8
The cross section has a substantially triangular mountain shape of 0 to 100 degrees and about 90 degrees in the present embodiment. Further, one of the screws 15 has a constant height H formed in the longitudinal direction at a constant height, in the present embodiment, about 0.03 to 0.055 mm. The other screw 16 has a height H1 at a portion near the lip tip 8 of the screw 16 and the constant height screw 15
The height H2 of the portion far from the lip tip 8 is higher than the low protruding portion 16a, and is 0.25 in this embodiment.
It is a high raised portion 16c formed to about mm, and is a stepped screw connected in the middle with a tapered portion 16b. The values θ1, θ2, H, H1, H2
May be determined based on the use conditions, the design concept, and the like, and are not particularly limited to the values of the present embodiment.

The screws 15 and 16 are formed by engraving portions corresponding to the screws 15 and 16 in a mold (not shown) used for vulcanization molding of the seal body 5 and vulcanization molding using the mold. It is formed by decision.

Next, the operation of this embodiment having the above-described configuration will be described.

According to the threaded oil seal 14 of the present embodiment, two types of plural spiral screws 15 connected to the lip tip 8 are provided on the radially inner seal surface 10 of the elastic seal lip 6. , 16 are alternately projected at the same pitch in the circumferential direction.
The desired area on the side comes into contact with the rotating shaft 2 in the mounted state.

In the initial stage of use in which the lip tip 8 is not worn or has a small amount of wear in contact with the rotating shaft 2, the constant height screw 15 and the stepped screw 1 are used.
6 is in contact with the rotating shaft 2 and the low-side protruding portion 16a contacts the sealed side OS.
, Which simultaneously causes a sealed fluid (not shown) to leak to the atmosphere side AS from the airtight side OS. As a result, a large pumping action is obtained by the sum of the low ridges 16a of the constant high screw 15 and the stepped screw 16, and the pump amount at the initial stage of wear of the lip tip 8 can be sufficiently maintained.

Thereafter, when the wear of the lip tip 8 further proceeds, the tapered portion 16b and the high raised portion 16c, which are higher than the low raised portion 16a of the stepped screw 16, gradually come into contact with the rotating shaft 2, so that The height of the screw 16 in contact with the rotating shaft 2 from the sealing surface 10 gradually increases, and a sealing fluid (not shown) that is leaking from the sealing side OS by the screw 16 toward the atmosphere side AS is always positioned on the sealing side OS. The pump action can be gradually increased, and stable sealing performance can be reliably maintained for a long period from the initial use of the oil seal.

Further, in this embodiment, since the constant high screws 15 and the step screws 16 are alternately arranged, the constant high screws 15 and the step screws 16 are evenly arranged in the circumferential direction. Therefore, the pump amount is also equal in the circumferential direction, and highly accurate sealing performance can be exhibited.

Next, referring to FIG. 5, the performance of the threaded oil seal 14 of the present invention will be described in comparison with the conventional example shown in FIG. 7 and the conventional example described in the publication shown in FIG.

FIG. 5 shows the change characteristics of the lip abrasion width and the amount of pump by the screw accompanying the use of the oil seal.

The measurement conditions in this case are as follows.
0 mm, the number of rotations was 3000 rpm, the oil to be sealed was engine oil 10W-30, and the oil temperature was 120 ° C. The lip wear width in FIG. 5 is the axial length of the inner peripheral surface 8a when the lip tip 8 of the seal lip 6 is worn, as shown in FIG.

Further, the shape, size, etc. of the constant height screw 15 and the stepped screw 16 of the present invention are as described above, and the conventional example of FIG. The same number as the total number of both screws 15 and 16 of FIG.
In the conventional example described in Japanese Patent Application Laid-Open No. 1-2003, the same number of stepped screws having the above-mentioned size are provided as the total number of one stepped screw 16 of the present invention.

FIG. 5 shows that the present invention maintains the same pump amount as in the conventional example shown in FIG. 7 even at the initial stage of use of the oil seal 14, but the conventional example described in the publication shown in FIG. It has been greatly reduced. Thereafter, as the use of the oil seal 14 progresses, the pump amount in the conventional example of FIG. 7 is greatly reduced, but the present invention can maintain a high pump amount similarly to the conventional example described in the publication shown in FIG. it can. Therefore, according to the present invention, it can be seen that stable sealing performance can be maintained for a long period of time from the initial use of the oil seal.

The present invention is not limited to the above embodiments, and may be changed as necessary, for example, by alternately arranging a plurality of fixed screws or stepped screws.

[0031]

As described above, according to the oil seal with a screw of the present invention, a simple structure can be used to provide a pump function for always positioning a sealing fluid that is leaking from the sealing side toward the atmosphere side on the sealing side. The oil seal can be maintained for a long period of time from the initial use of the oil seal, and has an extremely excellent effect that stable sealing performance can be reliably maintained for a long period of time.

Specifically, according to the first aspect of the present invention, in the initial stage of use when the unworn lip tip comes into contact with the counterpart, the constant high screw and the low ridge of the stepped screw come into contact with the counterpart so that the pump can be used. A sufficient pump amount can be obtained by reliably preventing a decrease in the amount, and as the wear of the lip tip progresses, the high protruding portion of the stepped screw gradually comes into contact with the counterpart, so that a sufficient pump amount can be obtained. . As a result, stable sealing performance can be maintained for a long period of time from the initial use of the oil seal.

According to the second aspect of the present invention, since the constant height screw and the stepped screw are evenly arranged in the circumferential direction, the pump amount is also equal in the circumferential direction, and a highly accurate sealing performance can be exhibited. it can.

[Brief description of the drawings]

FIG. 1 is a longitudinal half sectional view showing a main part of an embodiment of a threaded oil seal according to the present invention.

FIG. 2 is an enlarged sectional view showing a screw portion;

FIG. 3 is an enlarged sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is an enlarged sectional view taken along line 4-4 in FIG. 2;

FIG. 5 is a characteristic diagram showing a change characteristic of a lip wear width and a pump amount by a screw between an oil seal with a screw according to the present invention and two conventional examples.

FIG. 6 is an explanatory view showing a lip wear width in FIG. 5;

FIG. 7 is a longitudinal half sectional view showing a main part of a conventional oil seal with a screw;

FIG. 8 is an enlarged view showing a screw of a conventional oil seal with a screw;

FIG. 9 is an enlarged sectional view taken along line 9-9 in FIG. 8;

FIG. 10 is an enlarged sectional view taken along line 10-10 in FIG. 8;

FIG. 11 is a view similar to FIG. 2 showing another conventional example.

[Explanation of symbols]

 4 Reinforcement ring 5 Seal body 6 Seal lip 8 Lip tip 10 Seal surface 14 Threaded oil seal 15 Constant high screw 16 Stepped screw 16a Low ridge 16c High ridge AS Atmospheric side OS Sealed side θ1 (Screw) inclination angle θ2 Apex angle (of screw)

Claims (2)

[Claims] 1. A threaded oil seal comprising a plurality of helical screws protruding from a sealing surface connected to a tip of a lip, wherein the screw has a constant height screw whose height is constant in a longitudinal direction; Stepped portion having a low protruding portion whose height near the lip tip of the screw is substantially equal to the constant height screw and a high protruding portion whose height farther from the lip tip is higher than the low protruding portion An oil seal with a screw, characterized by being formed by a screw. 2. The threaded oil seal according to claim 1, wherein the constant height screw and the stepped screw are alternately arranged in a circumferential direction.