Seal member for rolling bearing and rolling bearing assembly

1. A seal member for a rolling bearing, the rolling bearing having a pair of inner rings fitted on a rotational shaft in such a state that axial end portions abut against each other, an outer ring disposed radially outwards of the pair of inner rings, and an annular groove provided on an outer circumference of a portion where the end portions of the pair of inner rings abut against each other,

wherein the seal member comprises an annular elastic portion made of an elastic material,

wherein the seal member is mounted in the annular groove,

wherein the elastic portion includes:

an annular proximal end portion that is fixed to one axial end side of the annular groove; and

an annular extending portion extending from the proximal end portion towards another axial end side of the annular groove, and having on an inner circumference thereof a sliding contact lip configured to be brought into sliding contact with the other axial end side of the annular groove,

wherein the extending portion includes:

a thin portion whose radial thickness is smaller than that of the proximal end portion along a circumferential direction, and which deforms radially outwards by virtue of a negative pressure generated in an interior of the rolling bearing to possibly cause the sliding contact lip to separate from the annular groove; and

a thick portion whose radial thickness is greater than that of the thin portion, and

wherein the thin portion and the thick portion are disposed alternately.

2. The seal member for a rolling bearing according to claim 1 , wherein the extending portion has a recess portion that opens at the other axial end side and whose depth direction follows an axial direction, and

wherein the thin portion is provided radially inwards of the recess portion.

3. The seal member for a rolling bearing according to claim 1 , wherein a sum of circumferential lengths of the thin portion is longer than a sum of circumferential lengths of the thick portion.

4. The seal member for a rolling bearing according to claim 1 , wherein a sum of circumferential lengths of the thin portion is shorter than a sum of circumferential lengths of the thick portion.

5. The seal member for a rolling bearing according to claim 1 , wherein a boundary portion between the thin portion and the proximal end portion is situated nearer to the one axial end side than an abutting plane where the end portions of the pair of inner rings abut against each other.

6. The seal member for a rolling bearing according to claim 1 , wherein a distal end portion of the thick portion on the other axial end side projects further towards the other axial end side than a distal end portion of the thin portion on the other axial end side.

7. The seal member for a rolling bearing according to claim 6 , wherein the distal end portion of the thick portion has a first sloping surface that comes to separate farther away from a bottom surface of the annular groove as the first sloping surface extends towards the other axial end side on a radially inner portion of the distal end portion,

wherein the distal end portion of the thin portion has a second sloping surface that comes to separate farther away from the bottom surface of the annular groove as the second sloping surface extends towards the other axial end side on a radially inner portion of the distal end portion, and

wherein an angle formed by the first sloping surface and the bottom surface of the annular groove is equal to or smaller than an angle formed by the second sloping surface and the bottom surface of the annular groove.

8. A rolling bearing assembly comprising:

the rolling bearing having the pair of inner rings, the outer ring, the annular groove, and a rolling element disposed between the outer ring and the inner rings; and

the seal member for the rolling bearing according to claim 1 ,

wherein the pair of inner rings has a first inner ring and a second inner ring whose end portions abut against each other in an axial direction of the inner rings,

wherein the annular groove is provided on an outer circumferential surface of a portion where the first inner ring and the second inner ring are caused to abut against each other, and

wherein the seal member for the rolling bearing is mounted in the annular groove.