Axle box suspension and elastic bushing shaft body for use in railcar

1. An axle box suspension of a railcar, the axle box suspension coupling an axle box to a bogie frame of a bogie including a wheel tread brake configured to press a wheel tread of a wheel from an inner side in a car longitudinal direction,

the axle box suspension comprising:

an axle beam including a beam portion and a tubular portion and coupling the axle box to the bogie frame, the beam portion extending in the car longitudinal direction from the axle box, the tubular portion being provided at a tip end of the beam portion and open toward both sides in a car width direction;

a core rod inserted into an internal space of the tubular portion and including a pair of protruding portions, the pair of protruding portions protruding toward both sides in the car width direction and being supported by the bogie frame; and

a tubular elastic bushing interposed between the tubular portion and the core rod, wherein:

the elastic bushing includes a recess at a portion of an outer peripheral surface of the elastic bushing which portion is located at the inner side in the car longitudinal direction, the recess being recessed outward in the car longitudinal direction;

the tubular portion includes a convex stopper portion protruding outward in the car longitudinal direction from a part of an inner peripheral surface of the tubular portion which part is located at the inner side in the car longitudinal direction, the stopper portion being inserted into the recess with a gap between the stopper portion and a bottom surface of the recess; and

a thickness of the elastic bushing at the recess in a radial direction is equal to or less than half a thickness of a portion of the elastic bushing in the radial direction which portion is located adjacent to the recess.

2. The axle box suspension according to claim 1 , wherein a maximum length of a tip end surface of the stopper portion in a surface direction of the tip end surface is 25% or more of an outer diameter of a portion of the core rod which portion is located at the same position as the recess in the car width direction.

3. An elastic bushing shaft body inserted into a tubular portion provided at a tip end of a beam portion of an axle beam in a bogie including a wheel tread brake configured to press a wheel tread of a wheel from an inner side in a car longitudinal direction, the axle beam coupling a bogie frame and an axle box, the beam portion extending from the axle box in the car longitudinal direction, the tubular portion being open toward both sides in a car width direction,

the elastic bushing shaft body comprising:

a core rod including a pair of protruding portions, the pair of protruding portions protruding toward both sides in the car width direction and being supported by the bogie frame; and

a tubular elastic bushing externally fitted to the core rod, wherein:

the elastic bushing includes a recess at a portion of an outer peripheral surface of the elastic bushing which portion is located at the inner side in the car longitudinal direction, the recess being recessed outward in the car longitudinal direction, a convex stopper portion being inserted into the recess with a gap between the stopper portion and a bottom surface of the recess, the stopper portion protruding outward in the car longitudinal direction from a part of an inner peripheral surface of the tubular portion which part is located at the inner side in the car longitudinal direction; and

a thickness of the elastic bushing at the recess in a radial direction is equal to or less than half a thickness of a portion of the elastic bushing in the radial direction which portion is located adjacent to the recess.

4. An axle box suspension of a railcar, the axle box suspension coupling an axle box to a bogie frame of a bogie including a wheel tread brake configured to press a wheel tread of a wheel from an inner side in a car longitudinal direction,

the axle box suspension comprising:

an axle beam including a beam portion and a tubular portion and coupling the axle box to the bogie frame, the beam portion extending in the car longitudinal direction from the axle box, the tubular portion being provided at a tip end of the beam portion and open toward both sides in a car width direction;

a core rod inserted into an internal space of the tubular portion and including a pair of protruding portions, the pair of protruding portions protruding toward both sides in the car width direction and being supported by the bogie frame; and

a tubular elastic bushing interposed between the tubular portion and the core rod, wherein:

the axle beam includes a stopper portion opposed in the car longitudinal direction to the core rod or a part of the bogie frame from the inner side in the car longitudinal direction with an open space between the stopper portion and the core rod or between the stopper portion and the part of the bogie frame; and

a size of the open space in the car longitudinal direction is smaller than a thickness of the elastic bushing.

5. The axle box suspension according to claim 4 , wherein:

the stopper portion protrudes in the car width direction from a part of the tubular portion which part is located at the inner side in the car longitudinal direction; and

the stopper portion is opposed in the car longitudinal direction to a portion of the core rod with the open space, the portion of the core rod projecting outward in the car width direction beyond the elastic bushing.

6. The axle box suspension according to claim 5 , wherein the stopper portion partially protrudes in the car width direction from the part of the tubular portion.

7. The axle box suspension according to claim 4 , wherein the elastic bushing is not in the open space.