Patent Description:
A sealing device that configured to seal an annular gap between a shaft and a housing that rotate relative to each other is known. For a sealing device that is used in a differential device, hub bearing, transmission and the like, a technique is known, in which a side lip is provided which is capable of sliding on an end face of an annular member fixed to a shaft, in addition to a seal lip that is capable of sliding on the shaft. A sealing device according to a conventional example is described with reference to <FIG> is a schematic cross-sectional view of a sealing device according to a conventional example.

A sealing device <NUM> according to a conventional example is provided with a seal lip <NUM> and a dust lip <NUM> which are capable of sliding on a shaft, and a side lip <NUM> capable of sliding on an end face of an annular member fixed to the shaft. The side lip <NUM> is configured to prevent dust or mud water from entering into the device. Lubricant (grease) is applied on a sliding surface of this side lip <NUM>. This effectively inhibits entrance of dust or mud water into the device.

In the sealing device <NUM> according to the conventional example configured as described above, the lubricant becomes depleted over time, whereby wear on the side lip <NUM> may be accelerated and noise may be generated.

Document <CIT> discloses a seal device having a main lip and a side lip. In the side lip there are dimples processed to keep grease.

Document <CIT> U suggests providing asymmetric protrusions in a main lip to overcome drawbacks known from the prior art. According to the prior art section of this document, a symmetrical prior art configuration having a triangle shape on a main lip requires improvement.

The object of the present disclosure is to provide a sealing device capable of suppressing depletion of lubricant. The object of the invention is achieved by a sealing device according to claim <NUM>. An advantageous embodiment is carried out according to claim <NUM>.

The present disclosure adopts following means to achieve the object noted above.

The sealing device of the present disclosure is a sealing device configured to seal an annular gap between a shaft and a housing that rotate relative to each other, the sealing device including:.

According to the present disclosure, the side lip is provided with a plurality of annular grooves on the sliding surface, so that the side lip can retain lubricant in the plurality of annular grooves. The lubricant is allowed to move between the annular grooves, because the parts that form annular protrusions between adjacent ones of these annular grooves all protrude most at the center in the width direction, the amount of protrusion gradually decreasing with increasing separation from the center. Therefore, depletion of lubricant in some of the annular grooves can be suppressed. Moreover, the parts that form annular protrusions between adjacent ones of the annular grooves are all symmetric in shape with respect to the center in the width direction, so that imbalance in the directions of movement can be minimized when the lubricant moves between the annular grooves. This configuration can prevent depletion of lubricant in some of the annular grooves even more reliably. Moreover, a tip portion of the sliding surface of the side lip on the distal side of a region provided with the plurality of annular grooves is configured to make a planar contact with an end face of the annular member. Therefore, entrance of mud water or the like into this contacting part is inhibited, and lubricant is prevented from flowing out.

Preferably, in a state where no external force is acting, the sliding surface of the side lip, except for the region thereof provided with the plurality of annular grooves, is formed by a conical surface.

As described above, according to the present disclosure, depletion of lubricant can be suppressed.

Modes for carrying out this disclosure will be described in detail hereinafter illustratively based on specific embodiments with reference to the drawings. It should be noted that, unless otherwise particularly specified, the sizes, materials, shapes, and relative arrangement or the like of constituent components described in the embodiments are not intended to limit the scope of this disclosure, the latter being limited only by the appended claims. The sealing device according to the present disclosure may be applied to a differential device, hub bearing, transmission, and the like.

A sealing device according to one embodiment of the present disclosure is described with reference to <FIG>. <FIG> is a cross-sectional diagram of the sealing device. <FIG> illustrates a cross section of the sealing device cut along a plane containing the center axis line of the sealing device. <FIG> is a schematic cross-sectional view of the sealing structure. <FIG> illustrates a cross section of the sealing device and others cut along a plane containing the center axis line of the sealing device and the shaft. <FIG> is an illustrative diagram of a side lip according to the embodiment of the present disclosure.

The sealing structure is described with reference, in particular, to <FIG>. The sealing structure is configured by a shaft <NUM> and a housing <NUM> that rotate relative to each other, and the sealing device <NUM> that seals an annular gap between the shaft <NUM> and the housing <NUM>. The sealing device <NUM> separates the annular gap between the shaft <NUM> and the housing <NUM>, so that the sealed fluid such as oil on the sealed side (O) is prevented from leaking to the outside (A), and dust or mud water is prevented from entering from the outside (A) into the sealed side (O). An annular member <NUM> that rotates with the shaft <NUM> is fixed to the shaft <NUM>. In a case where the sealing device (sealing structure) according to this embodiment is applied to a differential device, the annular member <NUM> corresponds to a deflector.

The sealing device <NUM> is described in more detail. The sealing device <NUM> includes a first component <NUM> and a second component <NUM>. The first component <NUM> is formed of a first reinforcing ring <NUM> made of metal or the like, and a seal main body <NUM> made of an elastic material such as rubber and formed integrally with the first reinforcing ring <NUM>. The first reinforcing ring <NUM> includes a cylindrical part <NUM> fitted and fixed to an inner circumferential surface of a shaft hole <NUM> of the housing <NUM>, and a body part <NUM> extending from one end of the cylindrical part <NUM> radially inward. The seal main body <NUM> is integrally provided to the radially inner side of the body part <NUM>.

The seal main body <NUM> integrally includes a seal lip (main lip) <NUM> and a dust lip <NUM>. The seal lip <NUM> extends from near the distal end of the body part <NUM> of the reinforcing ring <NUM> radially inward and toward the sealed side (O), and is capable of sliding on the shaft <NUM>. A garter spring <NUM> is mounted on the radially outer side of the seal lip <NUM> to press the seal lip <NUM> radially inward.

The dust lip <NUM> extends from near the distal end of the body part <NUM> of the reinforcing ring <NUM> radially inward and toward the opposite side (toward the outside (A)) from the sealed side (O) and is capable of sliding on the shaft <NUM>. The dust lip <NUM> mainly serves the function of preventing dust or mud water from entering into the seal lip <NUM> side.

The second component <NUM> is formed of a second reinforcing ring <NUM> made of metal or the like, and a side lip <NUM> made of an elastic material such as rubber and formed integrally with the second reinforcing ring <NUM>. The second reinforcing ring <NUM> includes a cylindrical part <NUM> fitted to an inner circumferential surface of the cylindrical part <NUM> of the first reinforcing ring <NUM>, and an inward flange part <NUM> extending from one end of the cylindrical part <NUM> radially inward. The side lip <NUM> is integrally provided near the distal end on the radially inner side of the inward flange part <NUM>. The side lip <NUM> extends from near the distal end of the inward flange part <NUM> radially outward and toward the opposite side (toward the outside (A)) from the sealed side (O) and is capable of sliding on an end face <NUM> of the annular member <NUM>. The side lip <NUM> serves the function of preventing dust or mud water from entering into the device (sealed side O). Lubricant (grease) G is applied on the sliding surface of the side lip <NUM>. This effectively inhibits entrance of dust or mud water into the device.

The side lip <NUM> is described in more detail with reference, in particular, to <FIG> and <FIG>. <FIG> illustrates a cross-sectional view V1 in a larger scale of an encircled part of the drawing (part near the distal end of the side lip <NUM>). <FIG> illustrates an enlarged cross-sectional view of the side lip <NUM> in a state where the side lip <NUM> is in contact with the end face <NUM> of the annular member <NUM>, and a diagram of relationship between the contact position and the contact surface pressure of the side lip <NUM> relative to the end face <NUM>. <FIG> also illustrates a cross-sectional view V2 in an even larger scale of the contacting part between the side lip <NUM> and the end face <NUM>, and an enlarged view V3 of the diagram of the contact surface pressure.

The sliding surface of the side lip <NUM> is provided with a plurality of annular grooves <NUM> adjacent each other at a position away from the distal end of the side lip <NUM>. The parts that form annular protrusions <NUM> between adjacent ones of the annular grooves <NUM> all protrude most at the center in the width direction, the protruding amount gradually decreasing away from the center. Both sides of the center in the width direction are symmetric in shape (see the enlarged view V2 in <FIG>). While the cross section of the annular protrusion <NUM> (cross section cut along a plane containing the center axis line of the sealing device <NUM>) has a circular arc outer shape in this embodiment, the cross section of the annular protrusion may have a triangular outer shape, or an oval-circular outer shape. A tip portion <NUM> of the sliding surface of the side lip <NUM> on the distal side of the region, which is provided with the plurality of annular grooves <NUM>, is configured to make a planar contact with the end face <NUM> of the annular member <NUM>.

In a state where no external force is acting, the part of the sliding surface of the side lip <NUM> except for the region provided with the plurality of annular grooves <NUM> is formed of a conical surface (commonly known as tapered surface). That is, the tip portion <NUM> mentioned above, and a portion to be a sliding surface in a region on the proximal side of the side lip <NUM> with respect to the region where the plurality of annular grooves <NUM> are provided, are both formed by a conical surface. More specifically, the tip portion <NUM> and the portion to be the sliding surface in the region on the proximal side of the side lip <NUM> with respect to the region, which is provided with the plurality of annular grooves <NUM>, are both located on the same imaginary conical surface. Moreover, the tips of all the plurality of annular protrusions <NUM> are located on the imaginary conical surface. In other words, on an inner circumferential surface of the side lip <NUM> formed of a conical surface (hereinafter referred to as "inner circumferential reference surface") are provided the plurality of annular grooves <NUM> as annular grooves recessed from the inner circumferential reference surface. Note that the present disclosure is not limited to this configuration. For example, the side lip may have a bent tip (see, for example, <CIT> mentioned above). The inner circumferential reference surface of the side lip <NUM> may not be formed of a conical surface. For example, the inner circumferential reference surface of the side lip in a cross section cut along a plane containing the center axis line may have a smoothly curved shape instead of a straight line as in the case of the conical surface. Although the plurality of annular grooves <NUM> are formed to be recessed from the inner circumferential reference surface and the tips of the annular protrusions <NUM> between adjacent ones of the annular grooves <NUM> are located on the inner circumferential reference surface which is an imaginary conical surface in the above described embodiment, the tips of the annular protrusions may be located outside, or inside, of the inner circumferential reference surface, which may be an inclined surface rather than a conical surface as mentioned above, while the inner circumferential reference surface is an imaginary conical surface in the embodiment described above.

The side lip <NUM> of the sealing device <NUM> according to this embodiment is provided with a plurality of annular grooves <NUM> on the sliding surface, so that the lubricant can be retained in the plurality of annular grooves <NUM>. The lubricant is allowed to move between the annular grooves <NUM>, because the parts that form annular protrusions <NUM> between adjacent ones of these annular grooves <NUM> all protrude most at the center in the width direction, the protruding amount gradually decreasing away from the center. Therefore, depletion of lubricant in some of the annular grooves <NUM> can be prevented.

The parts that form annular protrusions <NUM> between adjacent ones of the annular grooves <NUM> are all symmetric in shape with respect to the center in the width direction as illustrated in V2 of <FIG>. This makes the distribution of the contact surface pressure even on the left and right sides of the center where the surface pressure is highest as illustrated in V3 of <FIG>. This suppresses imbalance in the directions of movement when the lubricant moves between the annular grooves <NUM>. The details of this will be explained. The lubricant moves between the annular grooves <NUM> during operations that involves rotation of the annular member <NUM> with the shaft <NUM> or change in pressure between the side lip <NUM> and the end face <NUM> of the annular member <NUM> because of vibration in the axial direction or the like of the shaft <NUM>. If the distribution of surface pressure on the annular protrusions <NUM> is asymmetric on the left and right sides, the lubricant moves over to the slope with a smaller surface pressure gradient more easily, and moves over to the slope with a larger surface pressure gradient less easily. Consequently, the lubricant will move to a certain direction on the annular protrusions <NUM>, because of which the lubricant may be depleted in some of the annular grooves <NUM>. In this embodiment, as described above, the surface pressure distribution provided by the annular protrusions <NUM> is even on the left and right sides, so that imbalance in the directions of movement of the lubricant is minimized. Therefore, depletion of lubricant in some of the annular grooves <NUM> can be prevented even more reliably.

Moreover, in this embodiment, a tip portion <NUM> of the sliding surface of the side lip <NUM> on the distal side of the region where the plurality of annular grooves <NUM> are provided is configured to make a planar contact with the end face <NUM> of the annular member <NUM>. Therefore, entrance of mud water or the like into this contacting part is inhibited, and lubricant is prevented from flowing out.

Depletion of the lubricant can be suppressed by the sealing device <NUM> according to this embodiment. Since this in turn inhibits wear on the side lip <NUM>, noise generation can be prevented, and the durability of the sealing device <NUM> can be improved.

Claim 1:
A sealing device (<NUM>) configured to seal an annular gap between a shaft (<NUM>) and a housing (<NUM>) that rotate relative to each other, the sealing device (<NUM>) comprising:
a seal lip (<NUM>) configured to slide on the shaft (<NUM>); and
a side lip (<NUM>) configured to slide on an end face of an annular member (<NUM>) fixed to the shaft (<NUM>), wherein
the sealing device (<NUM>) being configured to be used in a state where lubricant is applied on a sliding surface of the side lip (<NUM>),
the sliding surface of the side lip (<NUM>) at a position away from a distal end of the side lip (<NUM>) is provided with a plurality of annular grooves (<NUM>) adjacent each other, each of all parts that form annular protrusions (<NUM>) between adjacent annular grooves (<NUM>) protrudes most at a center in a width direction thereof, with an amount of protrusion gradually decreasing with increasing separation from the center, both sides of the center in the width direction are symmetric in shape, and
a tip portion (<NUM>) of the sliding surface of the side lip (<NUM>) on a distal side of a region, which is provided with the plurality of annular grooves (<NUM>), is configured to make a planar contact with an end face (<NUM>) of the annular member (<NUM>).