JP2011074989A - Dynamic seal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dynamic seal enlarging the proper interference range of an axial lip and relatively facilitating the control of an interference. <P>SOLUTION: The dynamic seal 1 includes one axial lip 4 axially projecting in such a manner that the whole circumference contacts with a slide face 8 extending radially. The axial lip 4 in a free state not elastically deformed is bent to approach the slide face 8 as going outward in the radial direction R, and the axial lip 4 is formed so that the bent portion unbends little by little with increase of the interference. Since only after the bent portion unbends as the interference is increased and the cross section of the bent portion becomes almost straight, the other portion (part of the root) other than the end of the axial lip contacts with the slide face 8 and lip reaction force increases, the proper interference range of the axial lip 4 can be enlarged. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an improvement in an exercise seal having an axial lip that protrudes in an axial direction such that the entire circumference contacts a sliding surface extending in a radial direction.

As an example of an exercise seal having an axial lip that protrudes in the axial direction so that the entire circumference is in contact with the sliding surface extending in the radial direction and slides on the relatively rotating sliding surface to function as a dust seal There are hub seals (pack seals) used to prevent leakage of grease enclosed in the hub unit bearing that suspends the wheels of the wheel and to prevent external rainwater and mud from entering. .)
The shape of the axial lip in such a seal for movement is generally a conical surface (in the shape of a truncated cone) in a free state in which it is not elastically deformed, and its cross section is generally a linear shape (for example, (See Patent Documents 1 and 2.)
Further, in a configuration including two outer and inner axial lips (first axial lip and second axial lip), the sliding surface of the outer axial lip (slinger flange) is reduced in contact area. The purpose is to reduce the dynamic heat generation area and increase the pressing force, and to enlarge the space between the two axial lips to reduce the possibility of contact of these axial lips and improve the sealing effect. In some cases, the inner axial lip side of the outer axial lip is concave (see, for example, Patent Document 3).

Japanese Patent Laid-Open No. 2004-197913 JP 2009-168132 A JP 2009-024804 A

In the exercise seal having the axial lip, the tightening margin of the axial lip with respect to the sliding surface varies due to variations in dimensions of components such as an elastic member including the axial lip and a cored bar, and peripheral components, assembling errors, and the like.
In an exercise seal having a single axial lip, such as in Patent Documents 1 and 2, in which the cross section of the axial lip in a free state that is not elastically deformed is a linear shape, the appropriate margin range is narrow, There is a problem that it is difficult to manage.
For example, when the tightening allowance is larger than the proper tightening allowance range, the reaction force (lip reaction force) against the sliding surface of the axial lip increases rapidly, so that the rotational resistance and the amount of wear increase. In the case, the lip reaction force is rapidly reduced, so that the sealing effect is lowered.
In addition, if the tightening margin of the axial lip is large, a portion other than the tip of the lip (portion close to the root) comes into contact and wear progresses from this portion, so that the lip life is shortened.

A motion seal having two axial lips and a concave surface on the inner axial lip side of the outer axial lip as in Patent Document 3 achieves the above-mentioned certain purpose. There are two axial lips that slide, and the two axial lips have different shapes. Therefore, the variation in the dimensions of the two axial lips increases, and the two axial lips are affected by the tilt of the sliding surface. Variations in the lip tightening margin increase.
Therefore, similarly to the configuration having one axial lip as in Patent Documents 1 and 2, there is a problem that the appropriate tightening margin range of the axial lip is narrow and it is difficult to manage the tightening margin.
Further, in Patent Document 3, an axial lip in a free state that is not elastically deformed as in the configuration of the present invention to be described later is bent so as to approach the sliding surface as it goes outward in the radial direction. There is no disclosure of an exercise seal having one axial lip that is formed so as to be gradually extended as the tightening margin increases.

  In view of the above-described situation, the present invention intends to provide a motion seal that can widen the proper tightening margin range of the axial lip and relatively easily manage the tightening margin.

The exercise seal according to the present invention is an exercise seal having one axial lip projecting in the axial direction so that the entire circumference is in contact with the sliding surface extending in the radial direction in order to solve the above problem. The axial lip in a free state that is not elastically deformed is bent so as to approach the sliding surface as it goes outward in the radial direction, and the bent portion extends little by little as the tightening margin increases.
According to such a configuration, the axial lip is bent so as to approach the sliding surface as it goes outward in the radial direction in a free state that is not elastically deformed, and the bent portion gradually increases as the tightening margin increases. Since the axial lip is formed so as to extend, the bending part extends when the tightening margin is increased, and after the cross section of the bending part becomes substantially linear, other than the tip part of the axial lip (part of the root) ) Comes into contact with the sliding surface for the first time, and the lip reaction force increases, so that the appropriate tightening allowance range of the axial lip can be widened.
In addition, even when the tightening allowance is large, the wear can proceed sequentially from the tip of the lip, so compared with the case where improper wear proceeds such that stickiness occurs and wear proceeds from the base of the lip. As a result, it is possible to set a large wear allowance for the axial lip that greatly affects the mud-water resistance function, so that the life of the exercise seal can be extended.

  As described above, according to the exercise seal according to the present invention, the appropriate tightening allowance range of the axial lip can be widened, so that it is relatively easy to manage the tightening allowance, and the wear allowance of the axial lip is set large. This makes it possible to prolong the service life of the exercise seal.

It is a longitudinal cross-sectional side view which shows the hub unit bearing which uses the exercise | movement seal which concerns on embodiment of this invention. It is a vertical side view which expands and shows the principal part of the sticker for exercise concerning an embodiment of the invention, and (a) shows a case where an axial lip and a sliding surface are in a normal contact state and a tightening margin is small ( Similarly, b) shows a case where the tightening allowance is large in a normal contact state, and (c) shows a state where the tightening allowance is further large and a part of the base of the axial lip is in contact with the sliding surface. It is a vertical side view which shows the item for numerical analysis. It is a figure which shows the change of the lip reaction force by interference, Comprising: The case where the cross section of an axial lip is a linear shape, and the case where the cross section of an axial lip is a bending shape are shown in comparison. It is a figure which shows the change of the increase rate of the interference allowance by the curvature of the bending part of an axial lip. It is a vertical side view which shows the variation of the bending shape of an axial lip.

Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments shown in the accompanying drawings, and includes all embodiments that satisfy the requirements described in the claims. It is a waste.
Further, the rotational radial direction of the exercise seal 1 is referred to as a radial direction (see arrow R in the figure), and a view seen from the rotational axis direction (axial direction) of the exercise seal 1 is a front view.

FIG. 1 is a view for preventing leakage of grease enclosing an exercise seal 1 according to an embodiment of the present invention in a hub unit bearing 11 for suspending a wheel of an automobile, and preventing intrusion of external rainwater and mud. The example used as a hub seal (pack seal) used in Fig. 1 is shown.
The hub unit bearing 11 includes rolling elements 16, 16,... In which an inner ring 12 integrated with the rotation-side flange 14 and an outer ring 13 integrated with the fixed-side flange 15 are held by a cage (not shown). The inner ring 12 and the outer ring 13 are filled with grease (not shown) as a lubricant so as to close the annular opening between the inner ring 12 and the outer ring 13. The exercise seals 1, 1 having a substantially annular shape when viewed from the front are mounted.

As shown in FIG. 2, the exercise seal 1 according to the embodiment of the present invention is attached to an annular cored bar 2 having an L-shaped cross section that is fitted on the inner peripheral surface of the outer ring 13 of FIG. The sealing body 3 made of synthetic rubber or the like is vulcanized and bonded, and the sealing body 3 is provided with a lip structure including an axial lip 4, a radial lip 5 and an inner lip (dustrip) 6.
As the synthetic rubber, nitrile rubber (NBR), acrylic rubber (ACM), fluorine rubber (FPA) or the like is preferably used.

Further, as shown in FIG. 2, an annular slinger 7 having an L-shaped cross section made of a steel plate or the like is fitted on the outer peripheral surface of the inner ring 12 of FIG. 1, and is axially attached to a sliding surface 8 extending in the radial direction of the slinger 7. The lip 4 is in sliding contact, and the radial lip 5 is in sliding contact with the sliding surface 9 extending in the axial direction of the slinger 7.
Here, the axial lip 4 is for preventing foreign matter such as rainwater and mud from entering from the outside of the exercise seal 1, and the radial lip 5 is for preventing leakage of grease inside the hub unit bearing 11 and foreign matter from the outside. The inner lip 6 is for reducing the intrusion of foreign matter from the outside due to the labyrinth seal effect.

  Further, as shown in FIG. 2, the movement seal 1 has a larger outer diameter as the shape of one axial lip 4 protruding in the axial direction approaches the sliding surface 8 extending in the radial direction of the slinger 7. In a free state in which the axial lip 4 indicated by a two-dot chain line is not elastically deformed, the sliding surface 8 approaches the outer side in the radial direction. Thus, the cross section is bent in an arc shape, and the entire circumference of the tip of the axial lip 4 having such a shape is in sliding contact with the sliding surface 8.

In the exercise seal 1 having one axial lip 4 having such a shape, from the free state of the two-dot chain line in FIG. 2A, the solid line in FIG. 2A and the solid line in FIG. When the tightening margin is increased, the bending portion of the axial lip 4 is gradually extended as the tightening margin is increased, and even if the tightening margin is large as shown in FIG. Only is in contact with the sliding surface 8.
Further, if the tightening margin is further increased as shown in FIG. 2 (c), the bent portion of the axial lip 4 is further extended and the cross section of the bent portion becomes substantially linear. In this state, other than the tip portion of the axial lip 4 (A part of the root) contacts the sliding surface 8 for the first time.

  Therefore, even if the tightening allowance is increased until just before the state shown in FIG. It has a conventional axial lip, and has a movement seal in which the cross-section of the axial lip in a free state that is not elastically deformed is linear, and two conventional axial lips. Compared with the exercise seal having, the proper tightening margin range of the axial lip 4 can be widened.

  Further, the axial lip 4 is bent so as to approach the sliding surface 8 as it goes outward in the radial direction in a free state in which the elastic lip 4 is not elastically deformed. As compared with the case where improper wear occurs such that stickiness occurs and wear starts from the base of the lip, the wear allowance of the axial lip 4 that greatly affects the mud-water resistance function Can be set large, so that the life of the exercise seal 1 can be extended.

Next, an example of numerical analysis by FEM (Finite Element Method) will be described.
In the one axial lip 4 having the above-described shape that protrudes in the axial direction in a free state that is not elastically deformed as shown in FIG. 3, the lip thickness is t, and the distance from the tip of the bent portion to the root (the length of the straight line (string) S) was L, the radius of curvature of the bent portion was r, and the interference was A, and the numerical analysis was performed.

  Due to the change in the lip reaction force due to the tightening allowance A shown in FIG. 4, the axial lip 4 has a larger amount than the tightening allowance A1 at the point P1 immediately before the lip reaction force suddenly increases when the cross section of the axial lip 4 is linear. When the cross-section is bent, the tightening allowance A2 at the point P2 immediately before the lip reaction force suddenly increases is larger. Therefore, the axial lip 4 of the present invention is more effective than the exercise seal in which the cross-section of the axial lip 4 is linear. It can be seen that the exercise seal 1 in which the cross-section of the lip 4 has a bent shape can widen the appropriate tightening allowance range of the axial lip 4.

FIG. 5 is a diagram showing a change in the increase rate of the proper tightening range according to a dimensionless amount (L / r) corresponding to the curvature (1 / r) of the bent portion 4 of the axial lip. The case of a linear shape (L / r = 0) is 100%.
From FIG. 5, it can be seen that when L / r increases (when the curvature of the bent portion 4 increases), the appropriate tightening allowance range increases.
For example, when the cross section of the axial lip 4 is a straight shape (L / r = 0), when the cross section of the axial lip 4 is a bent shape, L / r = 0.5. About 20%, L / r = 1 is about 40%, and the proper tightening allowance range is widened.
In addition, under the condition that the bent portion of the axial lip 4 extends little by little as the tightening allowance A of the present invention increases, 0.3 <L / r <1.5 and 2 <L / t <30 is a desirable range.

In the above description, in a free state where the axial lip 4 is not elastically deformed, the cross section of the axial lip 4 is bent in an arc shape so as to approach the sliding surface 8 as it goes outward in the radial direction. However, the cross section of the axial lip 4 may have a shape that is refracted in multiple stages by combining straight lines as shown in FIG. 6, that is, the bent portion of the axial lip 4 is free of elastic deformation. In the state, it should be bent so as to approach the sliding surface 8 as it goes outward in the radial direction, and may be formed so as to gradually increase as the tightening margin increases.
In the above description, the configuration in which the exercise seal of the present invention is a hub seal (pack seal) is shown. However, the lip structure is not limited to the structure shown in FIG. The seal for use may be used for various purposes as long as it has an axial lip that protrudes in the axial direction so that the entire circumference is in contact with the sliding surface extending in the radial direction.

A Tightening margin L Length of straight line (string) from the tip of the bent part to the root r Radius of curvature R of the bent part 1 Radial direction 1 Seal for movement 2 Metal core 3 Sealing body 4 Axial lip 5 Radial lip 6 Inner lip 7 Slinger 8 , 9 Sliding surface 11 Hub unit bearing 12 Inner ring 13 Outer ring 14 Rotating flange 15 Fixed flange 16 Rolling element

Claims (1)

An exercise seal having one axial lip projecting in an axial direction so that the entire circumference is in contact with a sliding surface extending in a radial direction,
The axial lip in a free state that is not elastically deformed is bent so as to approach the sliding surface as it goes outward in the radial direction, and the bent portion extends little by little as the tightening margin increases. Exercise seal.

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