Railcar truck

1. A railcar truck that comprises a pair of side beams and that is configured to support a carbody, wherein:

each of the side beams includes:

a side beam outer wall located on an outer side in a railcar width direction and extending in a railcar-longitudinal direction;

a side beam inner wall located on an inner side with respect to the side beam outer wall in the railcar width direction and extending in the railcar-longitudinal direction;

a side beam lower wall extending in the railcar-longitudinal direction and on which is placed a secondary spring by which the carbody can be supported;

a side beam upper wall having an opening through which an upper portion of the secondary spring projects, the side beam upper wall extending in the railcar-longitudinal direction; and

a concavity that receives the secondary spring through the opening and that is formed by the side beam outer wall, the side beam inner wall, and the side beam lower wall,

for each of the side beams, a cross-sectional area of an opening-existing portion where the opening is formed is greater than a cross-sectional area of an opening-non-existing portion where the opening is not formed, and

in the opening-existing portion of each of the side beams, the railcar truck further comprises:

a first reinforcing member (i) located between the side beam outer wall and a center of the opening, (ii) spaced from the secondary spring, and (iii) extending from the side beam lower wall in a vertical direction;

a second reinforcing member (i) between the side beam inner wall and the center of the opening, (ii) spaced from the secondary spring, and (iii) extending from the side beam lower wall in the vertical direction;

the

a rectangular first closed cross-section formed by the side beam outer wall, the side beam upper wall, the first reinforcing member, and the side beam lower wall; and

a rectangular second closed cross-section formed by the side beam inner wall, the side beam upper wall, the second reinforcing member, and the side beam lower wall.

2. The railcar truck according to claim 1 , wherein in the opening-existing portion of each of the side beams:

at least two of the secondary springs are placed in the opening such that the secondary springs are adjacent to each other, and

a third reinforcing member extends along the railcar width direction between the secondary springs and is fixed to the side beam outer wall and the side beam inner wall.

3. The railcar truck according to claim 2 , further comprising a cross beam extending in the railcar width direction and connecting the pair of side beams to each other, wherein for each of the side beams:

a plurality of the openings are arranged along the railcar-longitudinal direction,

the concavity in at least one of the plurality of the openings includes the third reinforcing member, and

the cross beam is located at a position close to a said opening having the third reinforcing member.

4. The railcar truck according to claim 1 , wherein

the side beam lower wall on which the secondary spring is placed further has a drainage hole.

5. The railcar truck according to claim 1 , wherein

the distance between the first reinforcing member and the second reinforcing member in the railcar width direction is greater than the outer diameter of the secondary spring.

6. The railcar truck according to claim 1 , wherein bottommost surfaces of the first and second reinforcing members are coplanar with a bottommost surface of the secondary spring.

7. The railcar truck according to claim 1 , wherein the first reinforcing member and the second reinforcing member are spaced toward the center of the opening from surfaces of the side beam inner wall and the side beam outer wall that form the concavity.