JP3869058B2 - Oil seal - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an oil seal including a seal lip that is cantilevered so as to be swingable in and out of the radial direction. More specifically, the present invention relates to an oil seal having ribs that perform so-called pumping action that returns lubricating oil that is about to leak from a sliding contact portion between a shaft and a seal lip.
[0002]
[Prior art]
Conventionally, various oil seals for preventing leakage of lubricating oil have been considered. As an example, as shown in FIG. 9 and FIG. 10, in an oil seal 20 having a so-called triangular lip, the seal It is known that a so-called helix rib 23 that is inclined with respect to the axis is provided at a number of circumferences of the outer slope 22 of the lip 21.
[0003]
When the lubricating oil in the lubricating oil existing space leaks outward from the sliding contact portion with the shaft 24, the rib 23 causes the lubricating oil to be leaked to the lubricating oil existing space side as the shaft 24 rotates. Function to return. At this time, the returned lubricating oil is guided along one side wall surface of each rib 23. Such a returning action of the lubricating oil by the ribs 23 is called a pump action.
[0004]
Conventionally, the height of the rib 23 from the outer slope 22 of the seal lip 21 is set to be substantially constant, that is, equal to the entire length in the longitudinal direction. The outer slope 22 is conical and flat, and the ridge line at the top of the rib 23 is substantially parallel to the outer slope 22.
[0005]
[Problems to be solved by the invention]
By the way, in the conventional oil seal 20 having the above-described equal height ribs 23, when the seal lip and the ribs 23 are worn by sliding contact with the shaft 24, the tightening force of the garter spring 25 fitted on the seal lip 21 is fitted. As a result, the seal lip 21 is pressed against the shaft 24, so that the contact angle θ of the rib 23 with respect to the shaft 24 becomes larger than the initial contact angle θ ₀ as shown in FIG. The contact area of the rib 23 with the lubricating oil film 26 to be formed (see the hatched area in FIG. 11) gradually decreases.
[0006]
Thus, as the contact area of the rib 23 with the lubricating oil film 26 decreases, the pumping action by the rib 23 gradually decreases, and the return amount of the lubricating oil leaked toward the outer slope 22 decreases. This is confirmed by the applicant through experiments. That is, in the oil seal 20 of the conventional example, as the seal lip 21 and the rib 23 are worn, the effect of preventing the leakage of the lubricating oil is reduced and the sealing performance is lowered.
[0007]
Accordingly, an object of the present invention is to enable an oil seal to stably exhibit excellent sealing performance over a long period of time.
[0008]
[Means for Solving the Problems]
The oil seal of the present invention is an oil seal provided with a seal lip that is cantilevered so as to be swingable inward and outward in the radial direction. The inner diameter of the seal lip is reduced in diameter from the base side toward the free end side. In addition, a reduced-diameter slope that is partially in contact with the shaft having a circular cross section is provided, and the lubricating oil that is about to leak from the contact portion with the outer peripheral surface of the shaft is returned to the circumferential portion of the reduced-diameter slope. A rib having a triangular cross-section functioning as described above, the radius of curvature R ₁ of the ridgeline at the top of the rib is set smaller than the radius of curvature R ₂ of the reduced-diameter slope , and the curvature center O _{1 of the} rib is tapered and reduced in diameter. arranged on a straight line connecting the center of curvature O ₂ of the slope, the reduced径斜surface is set to the concave curved surface shape recessed radially outward such gradually decreases with the wear progresses, the contact angle with respect to the axis And the height of the rib from the reduced diameter surface is In order to gradually reduce the contact angle with respect to the axis of the shaft as the wear proceeds, the contact angle is gradually increased from the free end side toward the root side.
[0013]
In short, in the present invention, the inclination of the rib is devised in advance so that the contact angle of the rib with respect to the axis of the rib accompanying the progress of wear as in the prior art is anticipated so that the contact angle of the rib after wear is almost constant or small. -ing
[0015]
In the oil seal according to the first aspect, when the wear of the rib proceeds, the contact angle of the rib with respect to the shaft gradually decreases, and the contact area of the reduced diameter slope and rib with respect to the lubricating oil film formed on the outer peripheral surface of the shaft is gradually increased. Will be. Therefore, the pump action gradually increases as wear progresses.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The details of the present invention will be described with reference to implementation embodiments are shown in FIGS. 4-6. 1 to 3, 7, and 8 are embodiments as reference examples. The embodiment of the reference example shown in FIGS. 1 to 3 is the first embodiment, the embodiment according to the present invention shown in FIGS. 4 to 6 is the embodiment 2, and the embodiments of the reference examples shown in FIGS. The form is the third embodiment.
[0017]
1 to 3 relate to a first embodiment shown as a reference example . 1 is a longitudinal sectional view of the upper half of the oil seal, FIG. 2 is an enlarged view of a main part showing an initial use state, and FIG. 3 is an enlarged view of a main part showing a state after progress of wear. In the figure, 1 is a shaft having a circular cross section, and 2 is an oil seal.
[0018]
The oil seal 2 is formed by attaching an elastic body 4 such as rubber to an annular cored bar 3 having a substantially L-shaped radial section in the upper half so as to cover the inner and outer periphery thereof.
[0019]
In the elastic body 4, an inner peripheral portion of the annular cored bar 3 has a main seal lip 5 that is cantilevered so as to be swingable inward and outward in the radial direction, and an auxiliary seal lip that extends obliquely in a direction opposite to the main seal lip 5. 6 are integrally formed. A garter spring 7 is fitted on the outer periphery of the main seal lip 5 so as to press it against the outer peripheral surface of the shaft 1.
[0020]
The inner diameter of the main seal lip 5 is reduced in diameter from the base side toward the free end side and has a reduced diameter slope 51 that partially contacts the rotation shaft, and from the middle of the reduced diameter slope 51 to the free end side. A diameter-increasing slope 52 that increases in diameter is provided, and a crossing portion between both slopes 51, 52 is a tapered portion 53 having a minimum diameter. That is, the shape of the inner peripheral surface of the main seal lip 5 is substantially V-shaped in cross section. The inclination angle of the reduced-diameter slope 51 with respect to the axis 1 is set smaller than the inclination angle of the enlarged-diameter slope 52 with respect to the axis 1.
[0021]
The reduced-diameter slope 51 is a partially arc-shaped concave curved surface that is recessed outward in the radial direction, and ribs 8 having a substantially triangular cross-section are located at the circumference of the reduced-diameter slope 51 with respect to the axis. Inclined. The ridge line at the top of the rib 8 is set so as to be parallel to the reduced-diameter slope 51. Therefore, the height dimension of the rib 8 is set constant from the tapered portion 53 toward the root side. As the curve setting of the diameter-reduced slope 51 and the rib 8, for example, the center of curvature of the ridge line at the top of the rib 8 and the center of curvature of the diameter-reduced slope 51 are matched, and the height of the rib 8 is set to the rib 8. This can be done by setting the curvature radius R ₁ of the ridgeline at the top of the ridge line to be smaller than the curvature radius R ₂ of the reduced diameter slope 51.
[0022]
In such a configuration, even if the wear of the main seal lip 5 and the rib 8 progresses, as shown in FIG. 3, the contact angle θ of the rib 8 with respect to the shaft 1 remains substantially unchanged as the initial contact angle θ0. The contact area of the ribs 8 with respect to the lubricating oil film 9 formed on the outer peripheral surface (hatched portion in FIG. 3) is kept substantially constant. Therefore, regardless of the progress of wear of the main seal lip 5 and the rib 8, the required pumping action by the rib 8 can be stably continued for a long period of time. It will be possible to demonstrate stably over. However, the contact area of the rib with the lubricating oil film 9 is slightly smaller in the initial stage of use than after the progress of wear, but this is from the initial stage of use until the corner near the taper 53 is worn in the rib 8, and thereafter. Then, even if wear progresses, it becomes almost constant.
[0024]
4 to 6 are those according to the second embodiment of the oil seal of the present invention. In the second embodiment, as shown in the drawing, the height of the rib 8 from the reduced diameter inclined surface 51 is set to gradually increase toward the base side of the main seal lip 5. Specifically, the curvature radius R ₁ of the ridge line at the top of the rib 8 is set to be appropriately smaller than the curvature radius R ₂ of the reduced diameter slope 51, and the curvature center O ₁ of the rib 8 is set between the tapered portion 53 and the reduced diameter slope 51. They are arranged on a straight line L connecting the center of curvature O _2. In this case, as the wear of the rib 8 progresses, the contact angle θ of the rib 8 with respect to the shaft 1 gradually decreases, and the contact area of the rib 8 with the lubricating oil film 9 formed on the outer peripheral surface of the shaft 1 gradually increases. become. Therefore, the pump action by the rib 8 can be gradually increased as the wear of the rib 8 progresses.
[0025]
7 and 8 are those according to the third embodiment of the oil seal as a reference example.
[0026]
In the third embodiment, as shown in FIG. 7, the reduced-diameter slope 51 is flattened in a conical shape as in the conventional example, and the ridgeline at the top of the rib 8 is a concave polygon. In order to obtain such a concave polygon, the rib 8 is divided into a plurality of linear regions at a predetermined interval in the longitudinal direction, and the inclination angle with respect to the reduced diameter inclined surface 51 in each linear region is a region toward the root side by a predetermined amount. It should be set gradually larger.
[0027]
A design method for obtaining the aforementioned concave polygon will be described with reference to FIG. First, in an initial state, a straight line PS connecting the swing fulcrum P of the main seal lip 5 and the initial position S of the tapered portion 53 of the rib 8 is drawn. When the rib 8 is worn, the main seal lip 5 is tilted radially inward about the swing fulcrum P, so that the taper 53 of the rib 8 moves to the virtual position S ₁ in consideration of this fact. Then, the required position A point of the rib 8 comes into contact with the shaft 1. Thus, linear P-S ₁ is shifted by an angle alpha ₁ relative to the straight line P-S in the initial state, the contact angle of the rib 8 with respect to the axis 1 plus the offset angle alpha ₁ to the initial contact angle theta ₀ In order to maintain the initial contact angle θ ₀ , it is necessary to reduce the contact angle of the rib 8 by α ₁ while the point A of the rib 8 is in contact with the shaft 1. Therefore, the straight line AA ′ is set so that the angle between the point A and the extension line of the straight line AS is α ₁ . When the rib 8 is further worn, the tapered portion 53 moves from the virtual position S ₁ to the virtual position S _2, and the required position B point of the rib 8 comes into contact with the shaft 1. Thus, displaced linearly P-S ₂ is at an angle alpha ₂ relative to the straight line P-S in the initial state, the contact angle of the rib 8 with respect to the axis 1 becomes large as θ ₀ + α _2, the initial contact angle theta ₀ In order to hold it, it is necessary to reduce the contact angle of the rib 8 by α ₂ while the point B of the rib 8 is in contact with the shaft 1. Therefore, the straight line BB ′ is set so that the angle between the point B and the extension line of the straight line AS is α ₂ . Hereinafter, similarly, a straight line CC ′ is set according to the progress of wear. In the figure, in order to make it easy to visually recognize that the shape of the ridgeline at the top of the rib 8 is a polygon, the interval between the linear regions is set to be extremely large. For example, the shape of the ridgeline at the top of the rib 8 approximates a partial arc shape.
[0028]
In the case of the third embodiment, the contact angle θ of the rib 8 with respect to the shaft 1 accompanying the progress of wear becomes substantially unchanged with the initial contact angle θ _{0 in} a stepwise manner. The action can be kept almost constant. Of course, if the angle of each straight line area with respect to the straight line AS is gradually increased, the pumping action by the rib 8 can be gradually increased as in the second embodiment.
[0029]
(3) In the third embodiment , the reduced diameter inclined surface 51 may be a partially arcuate concave curved surface and a curved line.
[0030]
Above Symbol embodiments, the oil seal 2 having a main lip seal 5 of the so-called triangle but as an example, as long as it has at least reduced径斜surface 51, the present invention also oil seal any shape Can be applied.
[0031]
【The invention's effect】
In the invention of claim 1, as the wear progresses, the contact area of the rib with the lubricating oil film formed on the shaft can be gradually increased, so that the pumping action can be gradually increased and the excellent sealing performance can be exhibited. It becomes like this.
[0033]
Thus, according to the present invention, it is possible to provide a highly reliable oil seal that can exhibit excellent sealing performance over a long period of time.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an upper half of a first embodiment of an oil seal of a reference example . FIG. 2 is an enlarged view of a main part showing an initial use state of the seal lip of the first embodiment. Fig. 4 is an enlarged view of the main part of the oil seal according to the second embodiment of the present invention. Fig. 5 is an enlarged view of the main portion showing the initial use state of the seal lip of the second embodiment. FIG. 6 is an enlarged view of a main part showing a state after the progress of wear of the seal lip of Embodiment 2. FIG. 7 is a diagram corresponding to FIG. 2 of the oil seal of Embodiment 3 of the reference example . Fig. 9 is a longitudinal sectional view of the upper half of the conventional oil seal. Fig. 10 is an enlarged view of the main part showing the initial use state of the conventional seal lip. FIG. 11 is an enlarged view of the main part showing the state of the conventional seal lip after wear progress Description of]
1 Rotating shaft 2 Oil seal 5 Main seal lip 51 Reduced diameter slope of main seal lip 52 Expanded slope of main seal lip 53 Detail of main seal lip 8 Rib

Claims (1)

An oil seal having a seal lip that is cantilevered so as to be swingable inward and outward in the radial direction, the inner periphery of the seal lip being reduced in diameter from the base side toward the free end side and having a circular cross-section. A reduced-diameter slope that is partially in contact with the shaft is provided, and the circumferential portion of the reduced-diameter slope has a triangular cross-section that functions to return lubricating oil that is about to leak from the contact area with the outer peripheral surface of the shaft . ribs are provided, the radius of curvature R ₁ of the ridge line of the top portion of the rib is set smaller than the radius of curvature R ₂ of the reduced径斜surface, the center of curvature O ₁ of the rib, the center of curvature O ₂ of the tapered condensed径斜surface The reduced diameter slope is set to a concave curved shape that is recessed radially outward so that the contact angle with respect to the shaft gradually decreases as wear progresses, and from the reduced diameter surface Rib height dimension wears the contact angle to the rib axis An oil seal characterized by being set so as to gradually increase from the free end side toward the root side in order to be gradually reduced with progress.

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