JP2001027327A - Oil seal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a pump effect of a rib and to prevent problems such as lip breakage, under pressure of oil. SOLUTION: This oil seal forms a stepped rib 8 having high and low two steps on an outer tilt surface of a seal lip 1, at pressure sealing. In pressure sealing, by forming the rib 8 on the outer tilt surface of the seal lip 1, pump action pushing back lubricant to the inside of seal lip 1 at shaft rotating can be remarkably performed. The rib 8 is raised in a longitudinal direction at high and low two steps, and the length of a lower part of the rib 8 is set to be long or short according to the level of lubricant pressure, which can prevent the breakage of the lip at the time of shaft rotating caused by high pressure of the lubricant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil seal, and more particularly, to a pressure seal for bringing a seal lip into contact with a mating member by the pressure of lubricating oil.

[0002]

2. Description of the Related Art Conventionally, a pressure seal is constituted by a plain seal. As shown in FIG. 3, the plain seal is formed on the air-side slope 53 of the tapered portion 50 of the seal lip 51.
Are flat and no ribs are formed. In this plain seal, the tapered portion 50 is pressed from the rear side toward the outer peripheral surface 52A of the shaft 52 by the pressure of the oil 54 filled in the oil side.

FIG. 4 shows a helix seal.
This helix seal is formed by the tapered portion 6 of the seal lip 61.
A plurality of inclined ribs 65 are formed on the zero air-side inclined surface 63 at predetermined intervals in the circumferential direction. In the helix seal, a ring spring (not shown) is fitted in a concave portion 66 on the back surface of the tapered portion 60, and the tapered portion 60 is
A is to be pressed. In the helix seal, when the shaft 62 rotates, the lubricating oil 64 is pushed back to the oil side by the pumping action of the inclined rib 65, so that the dynamic sealing effect is high.

As described above, in a pressure seal in which a seal lip is pressed against a shaft by oil pressure, if a rib such as a helix seal is provided, the rib is pressed against the shaft with a strong pressure, and the shaft rotates. Occasionally, a malfunction such as a lip break may occur. Also, it was unconfirmed whether or not the pump effect by the rib could be exerted under pressure.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an oil seal which can exert a pumping effect of a rib even under the pressure of oil and which can avoid troubles such as lip breakage. is there.

[0006]

In order to achieve the above object, an oil seal according to the first aspect of the present invention has an oil seal having a seal lip which can be brought into contact with a mating member by the pressure of lubricating oil to be sealed. Ribs are provided at a plurality of circumferential positions on the outer slope of the seal lip, and the ribs are raised in a longitudinally stepped shape with two steps of height, and the ribs extend from the leading edge of the outer slope. It comprises a low portion extending by a predetermined dimension and a high portion extending from the low portion, and the length of the low portion is set to be long or short according to the level of the pressure of the lubricating oil. It is characterized by having.

According to the first aspect of the present invention, in the pressure seal, a stepped rib having two steps of height is formed on the outer slope of the seal lip, and the length of the lower part of the rib is adjusted according to the level of the pressure of the lubricating oil. It was set to long and short.

The inventors of the present invention have proposed that even in a pressure seal in which the seal lip is pressed against the shaft by the pressure of the lubricating oil, a rib is formed on the outer slope of the seal lip so that the inside of the seal lip is formed when the shaft rotates. It was confirmed that the pump action to push back the lubricating oil can be remarkably exhibited. Also, the rib is raised in two steps in the longitudinal direction,
By setting the length of the lower portion of the rib to be shorter or longer according to the level of the pressure of the lubricating oil, it was confirmed that lip breakage during shaft rotation caused by the high pressure of the lubricating oil can be prevented.

That is, when the working pressure is relatively high, the length of the rib lower portion is set to be relatively long, so that the lip break can be made difficult to occur. On the other hand, when the working pressure is relatively low, It was confirmed by an experiment that even when the length of the rib lower portion was relatively short, lip breakage was unlikely to occur.

Therefore, according to the oil seal of the present invention, even under oil pressure, by setting the length of the lower portion of the two-stage rib in accordance with the working pressure, the pump effect of the rib and prevention of lip breakage can be achieved. And can be compatible.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 1 shows an embodiment of an oil seal according to the present invention. This embodiment comprises an annular sealing lip 1. The seal lip 1 has a base 2 and a tapered portion 3 connected to the base 2. The taper 3 tapers radially inward. The tip 3A of the tapered portion 3 is slidably contacted with the outer peripheral surface 5A of the shaft 5. The tapered portion 3 has an air-side slope 6 as an outer slope and an oil-side slope 7 as an inner slope. The air-side inclined surface 6 protrudes into a plurality of two-stepped shapes extending from the tip 3A of the tapered portion 3 along the air-side inclined surface 6 by a predetermined dimension.
A step rib 8 is formed. The two-step rib 8 is inclined with respect to the axial direction.

The two-step rib 8 includes a low portion 11 extending from the tip 3A of the tapered portion 3 by a predetermined dimension L1 and a high portion 12 extending from the low portion 11 by a predetermined size L2. Become. The protruding dimension H1 at which the low portion 11 protrudes from the air-side inclined surface 6 is smaller than the protruding dimension H2 at which the high portion 12 protrudes from the air-side inclined surface 6, and is, for example, 1/5.
To the extent, is set. The low portion 11 is raised in a mountain shape having a substantially triangular cross section, and the high portion 12 is formed in the low portion 1.
It comprises a tapered portion 12A and a base portion 12B which taper toward 1. The tapered portion 12A of the high portion 12 has a substantially triangular pyramid shape that expands from the low portion 11 toward the base 12B, and the end of the wide end is connected to the base 12B. The base 12B also protrudes in a mountain shape having a substantially triangular cross section.

In this embodiment, the lower part 11 of the two-step rib 8 is used.
Is set to be approximately one half of the length L2 of the high portion 12. In this embodiment, the oil side of the tapered portion 3 of the seal lip 1 is filled with the lubricating oil 13.

In this embodiment, the two-stage rib 8 is formed according to the working pressure of the lubricating oil 13 so as to achieve the static sealing ability when the shaft is stationary and to prevent the occurrence of a lip break when the shaft rotates. The length L1 of the lower portion 11 is set to be longer or shorter.

Oil seal (pressure seal) of this embodiment
Then, the tapered portion 3 of the seal lip 1 is pressed against the outer peripheral surface 5 </ b> A of the shaft 5 by the pressure of the lubricating oil 13.
To the oil side of the taper 3.

When the shaft 5 rotates, the seal lip 1
Due to the pumping action of the two-stage rib 8 formed on the air-side inclined surface 6 of the tapered portion 3 of the tapered portion 3 so as to be inclined in the axial direction, the dynamic sealing performance when rotating the shaft is remarkably improved as compared with the case without the rib. it can.

In this embodiment, the seal lip 1
The lower part 1 of the two-step rib 8 is located in the area near the tip 3A of the tapered part 3
1 and the length L1 of the low portion 11 was set in accordance with the pressure of the lubricating oil 13, whereby the lip breakage phenomenon during rotation could be prevented.

For example, in the embodiment shown in FIG.
According to the pressure of 3, the length L1 of the low portion 11 of the two-stage rib 8 is set relatively short (shorter than the length L2 of the high portion 12), but the pressure of the lubricating oil 13 is higher. Figure 2
By setting the length L21 of the lower portion 21 of the two-stage rib 28 to be relatively long (substantially equal to the length L22 of the higher portion 22) as shown in FIG. Can be reliably prevented.

In the above embodiment, the two-stage rib 8 is raised in a triangular shape, but may be raised in a trapezoidal shape or a curved mountain shape.

[0021]

As is apparent from the above description, the oil seal of the present invention has a stepped rib having two high and low steps formed on the outer slope of the seal lip in the pressure seal, and the length of the low part is equal to that of the lubricating oil. The length is set in accordance with the level of the pressure.

The inventors of the present invention have confirmed that, in the pressure seal, by forming a rib on the outer slope of the seal lip, a pumping action that pushes lubricating oil back to the inside of the seal lip when the shaft rotates can be remarkably exhibited. Was. In addition, the rib is raised in two steps in the longitudinal direction, and the length of the low portion is set to be longer or shorter according to the level of the working pressure. I confirmed that it could be prevented. Therefore, according to the present invention, it is possible to realize an oil seal that can exert the pumping effect of the rib even under the pressure of the oil and that can avoid troubles such as lip breakage.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an embodiment of an oil seal of the present invention.

FIG. 2 is a sectional view of a main part showing a modification of the embodiment.

FIG. 3 is a sectional view of a main part of a plain seal as a conventional pressure seal.

FIG. 4 is a sectional view of a main part of a conventional helix seal.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Seal lip, 2 ... Base part, 3 ... taper, 3A ... Tip, 5 ... Shaft, 5A ... Outer peripheral surface, 6 ... Air side inclined surface, 8,2
8 ... two-step rib, 11,21 ... low part, 12,22 ... high part.

Claims (1)

[Claims] 1. An oil seal having a seal lip which is brought into contact with a mating member under the pressure of lubricating oil to be sealed, wherein ribs are provided at a plurality of circumferential positions on an outer slope of the seal lip. The rib protrudes in the longitudinal direction into a stepped shape having two steps of height, and a lower portion extending by a predetermined dimension from a leading edge of the outer slope, and extending from the lower portion. And the length of the lower part is determined according to the level of the pressure of the lubricating oil.
An oil seal characterized by being set to short or long.