Cage unit and tapered roller bearing equipped with cage unit

Provided is a cage unit including a cage having a small diameter side annular portion, a large diameter side annular portion arranged so as to be spaced apart in an axial direction from the small diameter side annular portion, and a plurality of cage bar portions that connect the small diameter side annular portion and the large diameter side annular portion; and a tapered roller accommodated in a pocket, which is a space surrounded by the small diameter side annular portion, the large diameter side annular portion, and the cage bar portions. A lubrication groove lying along a circumferential direction is formed on an inner end face of the large diameter side annular portion that faces a roller large end face of the tapered roller, and a circumferential length of the lubrication groove is designed such that the lubrication groove overlaps the roller large end face in the circumferential direction.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2014-062295 filed on Mar. 25, 2014 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a cage unit and a tapered roller bearing equipped with the cage unit. More specifically, the invention relates to a cage unit including a lubrication groove for accommodating lubricating oil, and a tapered roller bearing equipped with the cage unit.

2. Description of Related Art

A tapered roller bearing has been conventionally used to configure a rotation supporting unit of various types of mechanical devices. In such tapered roller bearing, a sliding portion exists between an end face of a tapered roller and a rib end face of an inner ring or an outer ring. A contacting state of both end faces in the sliding portion is a rolling contact that involves sliding. Thus, when the lubricating oil to be supplied to the bearing runs short or runs dry, seizure easily occurs at the end faces.

During the operation of the mechanical device, the lubricating oil is scattered and supplied to the bearing due to the stirring of the lubricating oil, and the like involved in the rotation of a shaft. If the mechanical device is once stopped but immediately re-started, the lubricating oil remaining on both end faces can maintain a lubricating effect, and hence the seizure does not occur.

However, if the mechanical device is once stopped and re-started after a considerable time has elapsed, the lubricating oil attached to both end faces flows down by gravity, and the lubricating oil runs short or runs dry. Thus, the seizure easily occurs.

Forming a groove for oil sump in a cage itself, which holds a plurality of tapered rollers at predetermined intervals along a circumferential direction, has been proposed (see e.g., Japanese Patent Application Publication No. 2007-32612 (JP 2007-32612 A)).FIG. 4Ais a partial perspective view of a cage20in a roller bearing described in JP 2007-32612 A.FIG. 4Bis a partial plan view of the same. In the cage20described in JP 2007-32612 A, a circumferential groove23that lies along a circumferential direction is formed on an inner end face21a, which faces a pocket22, of a large diameter end21of the cage20. The seizure is assumed to be prevented since the shortage of the lubricating oil at the time of an initial operation after a long idle period is alleviated by the lubricating oil accommodated in the circumferential groove23. InFIGS. 4A and 4B, a reference number24denotes a cage bar portion that connects a small diameter end25and the large diameter end21of the cage20.

As shown inFIG. 5, the circumferential groove23in the roller bearing described in JP 2007-32612 A is formed over the entire inner end face21afacing the pocket. Thus, portions23ain the vicinity of both ends of the circumferential groove23do not face the end face of the tapered roller26and are in an opened state. If an operation stopped state is continued for a long period of time, therefore, the lubricating oil flows out, though only gradually, from the portions23ain the vicinity of both ends of the circumferential groove23, whereby the lubricating oil may run short or run dry and the seizure may occur at the time of re-start.

SUMMARY OF THE INVENTION

One of the objects of the present invention is to provide a cage unit that can supply the lubricating oil even at the time of the initial operation after a long idle period and that can enhance a seizure resistance, and a tapered roller bearing equipped with the cage unit.

According to an aspect of the present invention, a cage unit includes a cage having a small diameter side annular portion, a large diameter side annular portion arranged so as to be spaced apart in an axial direction from the small diameter side annular portion, and a plurality of cage bar portions that connect the small diameter side annular portion and the large diameter side annular portion; and a tapered roller accommodated in a pocket, which is a space surrounded by the small diameter side annular portion, the large diameter side annular portion, and the cage bar portions. In the cage unit, a lubrication groove lying along a circumferential direction is formed on an inner end face of the large diameter side annular portion that faces a roller large end face of the tapered roller, and a circumferential length of the lubrication groove is designed such that the lubrication groove overlaps the roller large end face of the tapered roller in the circumferential direction.

DETAILED DESCRIPTION OF EMBODIMENTS

An embodiment of a cage unit and a tapered roller bearing equipped with the cage unit according to the present invention will be hereinafter described in detail with reference to the accompanying drawings.FIG. 1is a cross-sectional explanatory view of a tapered roller bearing1according to one embodiment of the present invention.FIG. 2is a perspective explanatory view of a cage2in the tapered roller bearing1shown in FIG.1.

The tapered roller bearing1according to the present embodiment includes an outer ring3, an inner ring4, a plurality of tapered rollers5, and the cage2. The outer ring3has a conical raceway surface3aon an inner circumferential side. The inner ring4has a conical raceway surface4a, which faces the raceway surface3a, on an outer circumferential side. The tapered rollers5are arranged in an annular space between the raceway surface3aand the raceway surface4a. The cage2holds the tapered rollers5at predetermined intervals along the circumferential direction. The cage2and the tapered rollers5configure a cage unit6. The inner ring4is arranged radially inwardly of the outer ring3so as to be relatively rotatable with respect to the outer ring3. A cone back face rib portion (hereinafter, referred to as a large rib portion)4bis formed on a large diameter side of the raceway surface4aof the inner ring4, and a cone front face rib portion (hereinafter, referred to as a small rib portion)4cis formed on a small diameter side of the raceway surface4a.

The cage2includes a small diameter side annular portion7, a large diameter side annular portion8, and a plurality of cage bar portions9. The large diameter side annular portion8is arranged so as to be spaced apart in an axial direction from the small diameter side annular portion7. The cage bar portions9connect the annular portions. As shown inFIG. 2, the cage2has a circular truncated cone shape as a whole, where a plurality of pockets10are formed at equal intervals along the circumferential direction between the cage bar portions9adjacent to each other. The tapered roller5is held in the pocket10in a freely rotating manner. The cage2can be produced from a synthetic resin that excels in oil resistance such as PPS containing glass fiber for example, but may also be produced from an iron-based metal.

A lubrication groove11that lies along the circumferential direction is formed on an inner end face8aof the large diameter side annular portion8of the cage2. The inner end face8aof the large diameter side annular portion8is the end face that faces a roller large end face5aof the tapered roller5so as to be contactable therewith. As shown inFIG. 3, a circumferential length of the lubrication groove11is designed such that the lubrication groove11overlaps the roller large end face5aof the tapered roller5in the circumferential direction e.g. as shown the lubrication groove is opposite the roller large end face over the entire length of the lubrication groove so that it can be covered by end face5a. Thus, when the device equipped with the tapered roller bearing1is stopped, an opening of the lubrication groove11is brought into contact with the roller large end face5aof the tapered roller5as if being covered by the roller large end face5a. In other words, the lubricating oil is held between the roller large end face5aof the tapered roller5and the cage2by a surface tension of the lubricating oil. Therefore, even if the device is re-started after a long idle period, the lubricating oil accommodated in the lubrication groove11will not flow out. As a result, the seizure at the time of the re-start that occurs from the shortage or the depletion of the lubricating oil can be prevented.

As shown inFIG. 3, the lubrication groove11in the present embodiment is positioned on a radially outer side (upper side inFIG. 3) of a pitch circle C of the roller large end face5aof the tapered roller5. The lubrication groove11has a short side11aextending in a circumferential direction, a long side11b, and coupling sides11c. The long side11bis positioned on the radially inner side of the short side11a, and has a longer circumferential length than the short side11a. The coupling sides11cconnect the ends of the short side11aand the long side11b. The opening of the lubrication groove11surrounded by the short side11a, the long side11b, and the coupling sides11chas a substantially trapezoidal shape. The coupling side11cis a curved line (circular arc) substantially parallel to an edge5b, that is, a circular edge of the roller large end face5aof the tapered roller5. Thus, a minimum thickness can be made thick and molding can be made advantageous, and furthermore, the capacity of the lubrication groove11can be increased.

In the present embodiment, a circumferential length w between the coupling side11cand the edge of the roller large end face5aof the tapered roller5is set to be longer than a relatively movable distance in the circumferential direction of the tapered roller5and the pocket10. Therefore, even if the tapered roller5is stopped and deviated to either side in the circumferential direction in the pocket10, the opening of the lubrication groove11can be reliably covered by the roller large end face5aof the tapered roller5. Thus, the lubricating oil can be reliably prevented from flowing out from the lubrication groove11. The circumferential length w between the coupling side11cand the edge of the roller large end face5aof the tapered roller5is not particularly limited in the present invention, and may be about 0.5 mm, for example.

The lubrication groove11is arranged at substantially the middle of the inner end face8aof the large diameter side annular portion8in each of the height direction (up and down direction inFIG. 3) and the circumferential direction. A height h1of the lubrication groove11is about a third of a height h2of the inner end face8a. A length L1of the short side11aof the lubrication groove11along the circumferential direction is about two thirds of a length L2of the inner end face8aalong the circumferential direction. The size and depth of the opening of the lubrication groove11are not particularly limited in the present invention, and may be appropriately selected within a range so that a predetermined strength is ensured in view of the material, the size, and the like of the cage2.

The embodiment disclosed herein is to be considered in all aspects as merely illustrative and not restrictive. The scope of the invention is defined by the appended claims rather than by the foregoing detailed description of the embodiment.

For example, the shape of the opening of the lubrication groove is a substantially trapezoidal shape in the embodiment described above, but may be other shapes such as an oval shape, and a band plate shape. Furthermore, the coupling sides that connect the short side and the long side of the lubrication groove are curved lines in the embodiment described above, but may be straight lines.

According to the cage unit and the tapered roller bearing equipped with the cage unit of the present invention, the lubricating oil can be supplied even at the time of the initial operation after a long idle period, and the seizure resistance can be enhanced.