Sealing structure

A sealing structure that allows for formation of a side lip, as well as a labyrinth structure between an oil seal and a torsional vibration damper, even when a reinforcing ring has a short inward flange part. The sealing body 120 includes a side lip 124 extending from near a distal end of an inward flange part 112 of the reinforcing ring 110 radially inward and further toward an air side (A) than a dust lip 122 to a position not as far as the outer circumferential surface of a tubular part 210. The tubular part 210 includes a small-diameter part 211 on which the dust lip 122 slides, and a large-diameter part 212 on the air side (A). The large-diameter part 212 has a tapered surface 212a formed on an outer circumferential surface thereof that reduces in diameter toward the air side (A). An annular gap S is formed between this tapered surface 212a and an inner circumferential surface of the side lip 124.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/JP2015/081261, filed Nov. 6, 2015 (now WO 2016/080203 A1), which claims priority of Japanese Application No. 2014-233304, filed Nov. 18, 2014. The entire disclosures of each of the above applications are incorporated herein by reference.

FIELD

The present disclosure relates to a sealing structure that has a torsional vibration damper.

BACKGROUND

A technique has hitherto been known which minimizes the entrance of foreign substances from outside into a sealing structure that has a torsional vibration damper and an oil seal, by providing a labyrinth structure in the sealing structure. One example of such a structure will be described with reference toFIG. 3.FIG. 3is a schematic cross-sectional view of a sealing structure according to a prior art example.

As shown, the torsional vibration damper600includes a tubular part610that is attached to a crankshaft300. The oil seal500includes a reinforcing ring510and a sealing body520made of an elastic material and formed integrally with the reinforcing ring510. The reinforcing ring510includes a cylindrical part511, and an inward flange part512provided at an end on the opposite side from the sealed-fluid side of this cylindrical part511. The sealing body520includes an oil lip521provided such as to be slidable on an outer circumferential surface of the tubular part610, and a dust lip522provided further on the opposite side from the sealed-fluid side than the oil lip521and slidable on the outer circumferential surface of the tubular part610.

In addition, a side lip523is provided to the sealing body520in this prior art example. This side lip523is configured to increase in diameter toward the opposite side from the sealed-fluid side so that foreign substances do not easily enter the sliding part between the dust lip522and the outer circumferential surface of the tubular part610from the air side. An annular groove621is formed in a body part620of the torsional vibration damper600. The side lip523is disposed such as to extend into this annular groove621. This way, a confined and complex path is formed from the air side to the sliding part between the dust lip522and the outer circumferential surface of the tubular part610. A labyrinth structure is thus provided.

In some cases where there is only a small space available for mounting the oil seal500, the inward flange part512of the reinforcing ring510has to be made shorter. In such cases, it may not be possible to adopt the side lip523configured as described above. The reason therefor is explained below.

The oil seal500is fabricated by insert-molding the sealing body520, with the reinforcing ring510serving as the insert component. In this process, the sealing body520is formed, with the reinforcing ring510being set in position in the metal mold. The resultant sealing body520has an opening524, which leads to an end face of the inward flange part512of the reinforcing ring510on the opposite side from the sealed-fluid side. That is, the opening524is formed in a portion corresponding to a support part (not shown) provided in the metal mold for the positioning purpose. Therefore, the portion on the end face of the inward flange part512of the reinforcing ring510on the opposite side from the sealed-fluid side is exposed. This exposed portion is utilized when mounting the oil seal500. Namely, when mounting the oil seal500, it is pressed with a jig or the like. If the sealing body520that is made of an elastic material is pressed, it may be damaged or broken, so that the reinforcing ring510is pressed instead, through the opening524.

If the inward flange part512of the reinforcing ring510is short and the side lip523is configured to increase in diameter toward the opposite side from the sealed-fluid side, the opening524may be blocked by the side lip523. If this is the case, the reinforcing ring510cannot be pressed with a jig or the like through the opening524.

During transportation, a plurality of oil seals500are stacked on one another along the center axis direction. In the case with the oil seal500shown inFIG. 3, when a plurality of the oil seals500are stacked on one another, the side lips523fit in the annular gaps between the oil lips521and the cylindrical parts511of the reinforcing rings510of adjacent oil seals500. Thus the plurality of oil seals500can be snugly stacked on one another. However, if the inward flange part512of the reinforcing ring510is short and the side lip523is configured to increase in diameter toward the opposite side from the sealed-fluid side, the side lip523may, depending on size, abut a portion of the reinforcing ring510of the adjacent oil seal500, near the distal end of the cylindrical part511of the reinforcing ring510. In this case, the plurality of oil seals500cannot be stacked on one another.

Further, the body part620of the torsional vibration damper600needs to be sufficiently thick so as to form the annular groove621for providing the labyrinth structure. This increases the weight of the body part620of the torsional vibration damper600. Also, since the body part620is typically a cast product so that the annular groove621has to be formed by a cutting process, which is another impediment to cost reduction.

CITATION LIST

Patent Literature

SUMMARY

Technical Problem

An object of the present disclosure is to provide a sealing structure that allows for formation of a side lip, as well as a labyrinth structure between an oil seal and a torsional vibration damper, even when the reinforcing ring has a short inward flange part.

Solution to Problem

The present disclosure adopted the following means to solve the problem noted above.

Namely, the sealing structure of the present disclosure is a sealing structure including a torsional vibration damper having a tubular part to be attached to a crankshaft, and an oil seal that seals an annular gap between an inner circumferential surface of a shaft hole in a housing for the crankshaft to pass through and an outer circumferential surface of the tubular part.

The oil seal includes a reinforcing ring having a cylindrical part, and an inward flange part provided at an end on an opposite side from a sealed-fluid side of the cylindrical part, and a sealing body made of an elastic material and provided integrally with the reinforcing ring.

The reinforcing ring is configured such that a portion on an end face of the inward flange part on the opposite side from the sealed-fluid side is exposed.

The sealing body includes an oil lip extending from near a distal end of the inward flange part toward the sealed-fluid side and slidable on the outer circumferential surface of the tubular part, a dust lip extending from near the distal end of the inward flange part toward the opposite side from the sealed-fluid side and slidable on the outer circumferential surface of the tubular part, and a side lip extending from near the distal end of the inward flange part radially inward and further toward the opposite side from the sealed-fluid side than the dust lip to a position not as far as the outer circumferential surface of the tubular part.

The tubular part includes a small-diameter part on which the dust lip slides, and a large-diameter part on an opposite side from the sealed-fluid side of the small-diameter part.

An outer circumferential surface of the large-diameter part includes a tapered surface that reduces in diameter toward the opposite side from the sealed-fluid side. An annular gap is formed between the tapered surface and an inner circumferential surface of the side lip.

According to the present disclosure, the side lip extends from near the distal end of the inward flange part of the reinforcing ring radially inward and further toward the opposite side from the sealed-fluid side than the dust lip to a position not as far as the outer circumferential surface of the tubular part of the torsional vibration damper. Therefore, even if the inward flange part of the reinforcing ring is short, the exposed portion on the end face on the opposite side from the sealed-fluid side of the inward flange part will not be blocked by the side lip. Accordingly, when mounting the oil seal, the inward flange part can be pressed directly by a jig or the like. Even when a plurality of oil seals are stacked on one another along the center axis direction, their side lips will not abut a portion of the reinforcing ring of adjacent oil seals, near the distal end of the cylindrical part of the reinforcing ring.

An annular gap is formed between the tapered surface formed on the outer circumferential surface of the large-diameter part provided to the tubular part of the torsional vibration damper and the inner circumferential surface of the side lip. This way, a confined and complex path is formed from the opposite side from the sealed-fluid side to a sliding part between the dust lip and the outer circumferential surface of the small-diameter part of the tubular part. Namely, a labyrinth structure can be provided. As described above, according to the present disclosure, even when the reinforcing ring has a short inward flange part, a side lip can be formed, and also a labyrinth structure can be provided between the oil seal and the torsional vibration damper.

The outer circumferential surface of the large-diameter part provided to the tubular part of the torsional vibration damper is formed of a tapered surface that reduces in diameter toward the opposite side from the sealed-fluid side. This way, entrance of dirt or the like into the annular gap between the outer circumferential surface of the large-diameter part of the tubular part and the side lip can be minimized.

The inner circumferential surface of the side lip should preferably be formed of a tapered surface with a taper angle substantially equal to a taper angle of the tapered surface formed on the large-diameter part.

This allows the distance from one end to the other end of the annular gap to be made long, with a small spacing between the outer circumferential surface of the large-diameter part of the tubular part and the side lip. This way, entrance of dirt or the like into the sliding part between the dust lip and the outer circumferential surface of the small-diameter part of the tubular part can be minimized more reliably.

Advantageous Effects of the Disclosure

As described above, according to the present disclosure, even when the reinforcing ring has a short inward flange part, a side lip can be formed, and also a labyrinth structure can be provided between the oil seal and the torsional vibration damper.

DETAILED DESCRIPTION

Modes for carrying out this disclosure will be hereinafter illustratively described in detail based on a specific embodiment 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 embodiment are not intended to limit the scope of this disclosure.

Embodiment

The sealing structure according to an embodiment of the present disclosure will be described with reference toFIG. 1andFIG. 2.FIG. 1is a schematic cross-sectional view of the sealing structure according to the embodiment of the present disclosure. It is a cross-sectional view of a plane that contains the center axis of a crankshaft.FIG. 1shows a simplified form of a torsional vibration damper.FIG. 2is a schematic cross-sectional view of an oil seal according to the embodiment of the present disclosure. It is a cross-sectional view of a plane that contains the center axis of the oil seal, which has a substantially rotationally symmetrical shape.

The overall configuration of the sealing structure according to this embodiment will be described with reference toFIG. 1in particular. The sealing structure according to this embodiment includes an oil seal100, a torsional vibration damper200attached to a crankshaft300, and a front cover400as a housing.

The torsional vibration damper200is an energy absorbing device attached to the crankshaft300for preventing the torsional vibration amplitude from becoming too large. The torsional vibration damper200has an annular body part220and a cylindrical tubular part210on the inner peripheral side of the body part220to be attached to the crankshaft300. An annular weight230made of metal, and an annular elastic member240made of an elastic material such as rubber for coupling the body part220and the annular weight230are provided on the outer peripheral side of the body part220. These annular weight230and annular elastic member240provide the function of restricting the torsional vibration amplitude of the crankshaft300.

The oil seal100serves the function of sealing an annular gap between the inner circumferential surface of a shaft hole in the front cover400for the crankshaft300to pass through and the outer circumferential surface of the tubular part210of the torsional vibration damper200. More specifically, the oil seal100serves the function of minimizing leakage of oil, which is a fluid to be sealed, from a sealed-fluid side (O) to an air side (A) that is the opposite side from the sealed-fluid side (O), and of minimizing entrance of foreign substances such as dust or dirt from the air side (A) to the sealed-fluid side (O).

The oil seal100will be described in more detail with reference toFIG. 1andFIG. 2. The oil seal100includes a metal reinforcing ring110and a sealing body120made of an elastic material such as rubber and formed integrally with the reinforcing ring110. The oil seal100can be obtained by forming the sealing body120by insert molding, with the reinforcing ring110as the insert component.

The reinforcing ring110includes a cylindrical part111and an inward flange part112provided at an end on the air side (A) of the cylindrical part111. The sealing body120integrally includes an oil lip121and a dust lip122that are slidable on the outer circumferential surface of the tubular part210of the torsional vibration damper200, an outer circumferential sealing portion123that makes tight contact with an inner circumferential surface of the shaft hole in the front cover400, and a side lip124.

The oil lip121is formed to extend from near the tip of the inward flange part112of the reinforcing ring110radially inward toward the sealed-fluid side (O). A plurality of thread grooves121aare formed in the inner circumferential surface of the oil lip121, which provide the pumping effect for returning leaked oil back to the sealed-fluid side (O). In addition, a garter spring130is mounted on the outer circumferential side of this oil lip121for applying a force radially inward so that the oil lip121will not separate from the outer circumferential surface of the tubular part210. The dust lip122is formed to extend from near the tip of the inward flange part112radially inward toward the air side (A).

The side lip124according to this embodiment is formed to extend from near the tip of the inward flange part112radially inward and further toward the air side (A) than the dust lip122to a position not as far as the outer circumferential surface of the tubular part210.

The sealing body120is formed with openings125. The plurality of openings125are circumferentially spaced from each other. As described in conjunction with the background art, the plurality of openings125are formed in portions corresponding to support portions (not shown) provided in the metal mold for the positioning purpose during insert molding. These openings125expose parts of the end face on the air side (A) of the inward flange part112of the reinforcing ring110.

The labyrinth structure provided in the sealing structure according to this embodiment will be described with reference toFIG. 1in particular. In this embodiment, the tubular part210of the torsional vibration damper200is made up of a small-diameter part211on the sealed-fluid side (O) and a large-diameter part212nearer to the air side (A) than this small-diameter part211. The oil lip121and dust lip122of the oil seal100slide on the small-diameter part211of the tubular part210. The outer circumferential surface of the large-diameter part212of the tubular part210is formed as a tapered surface212athat reduces in diameter toward the air side (A). An annular gap S is formed between this tapered surface212aand the inner circumferential surface of the side lip124.

With the annular gap S thus provided, a confined and complex path is formed from the air side (A) to a sliding part between the dust lip122and the outer circumferential surface of the small-diameter part211of the tubular part210. A labyrinth structure is thus provided.

The inner circumferential surface of the side lip124is also formed as a tapered surface124a. It goes without saying that the annular gap S mentioned above is formed even when the taper angle of the tapered surface124aof this side lip124is different from the taper angle of the tapered surface212aof the large-diameter part212of the tubular part210. However, if these taper angles differ from each other, the spacing of the annular gap S will be increasing gradually either from the sealed-fluid side (O) to the air side (A), or from the air side (A) to the sealed-fluid side (O). It will therefore be harder to make the distance from one end to the other of the annular gap S long while keeping a small spacing.

In this embodiment, therefore, the inner circumferential surface of the side lip124is formed as a tapered surface124awith substantially the same taper angle as that of the tapered surface212aof the large-diameter part212of the tubular part210. As both members are designed to be tapered at an equal angle, their taper angles are substantially equal. This way, the distance from one end to the other of the annular gap S can be made long while keeping a small spacing.

With such a labyrinth structure provided, entrance of foreign substances such as dust or dirt into the sliding part between the dust lip122and the outer circumferential surface of the tubular part210can be minimized without involving an increase in torque. Thus the sealing function provided by the oil seal100can be consistently exhibited for a long time.

<Advantages of the Sealing Structure According to this Embodiment>

According to the sealing structure of this embodiment, the side lip124is configured to extend from near the distal end of the inward flange part112of the reinforcing ring110radially inward and further toward the air side (A) than the dust lip122to a position not as far as the outer circumferential surface of the tubular part210of the torsional vibration damper200. Therefore, even if the inward flange part112of the reinforcing ring110is short, the openings125formed in the sealing body120will not be blocked by the side lip124. That is, the exposed portions on the end face on the air side (A) of this inward flange part112will not be blocked by the side lip124. Accordingly, when mounting the oil seal100, the inward flange part112can be pressed directly by a jig or the like. Namely, the oil seal100is mounted into the shaft hole in the front cover400by being pressed with a jig or the like from the left side ofFIG. 1. In this embodiment, the metal inward flange part112is pressed directly by a jig or the like through the openings125, so that the sealing body120made of an elastic material will not be damaged or broken.

Even when a plurality of oil seals100are stacked on one another along the center axis direction, their side lips124will not abut a portion of the reinforcing ring110of adjacent oil seals100, near the distal end of the cylindrical part111of the reinforcing ring110. Therefore, the oil seals100according to this embodiment can be stacked on one another along the center axis direction.

Furthermore, in the sealing structure according to this embodiment, an annular gap S is formed between an outer circumferential surface (tapered surface212a) of the large-diameter part212of the tubular part210and the inner circumferential surface of the side lip124. This annular gap S provides a labyrinth structure. Therefore, with the sealing structure according to this embodiment, even when the inward flange part112of the reinforcing ring110is short, a side lip124can be provided, and a labyrinth structure can also be provided between the oil seal100and the torsional vibration damper200. A labyrinth structure can thus be provided even without providing an annular groove in the torsional vibration damper, which generally involves cumbersome processing. Since it is not necessary to provide an annular groove in the body part220of the torsional vibration damper200, the thickness of the body part220can be reduced. This enables a reduction in weight of the body part220. In the case with this embodiment, it is only necessary to provide a step on the tubular part210(i.e., to form the tubular part210from a small-diameter part211and a large-diameter part212). Even when the tubular part is fabricated by casting, no cutting process is necessary, so that the production cost can be reduced.

The outer circumferential surface of the large-diameter part212provided to the tubular part210of the torsional vibration damper200is formed as a tapered surface212athat reduces in diameter toward the air side (A). This way, entrance of dirt or the like into the annular gap S between the outer circumferential surface of the large-diameter part212of the tubular part210and the side lip124can be minimized. Dirt or the like that came down accumulates near the portion indicated with arrow X inFIG. 1(boundary between the body part220and the large-diameter part212), and as the crankshaft300rotates, the dirt drops further down inFIG. 1. Thus entrance of dirt or the like into the annular gap S can be minimized.

Moreover, in this embodiment, the inner circumferential surface of the side lip124is formed as a tapered surface124awith substantially the same taper angle as that of the tapered surface212aof the large-diameter part212of the tubular part210. This allows the distance from one end to the other end of the annular gap S to be made long, with a small spacing between the outer circumferential surface of the large-diameter part212of the tubular part210and the side lip124. This way, entrance of dirt or the like into a sliding part between the dust lip122and the outer circumferential surface of the small-diameter part211of the tubular part210can be minimized more reliably.

REFERENCE SIGNS LIST