Load measuring device for railcar bogie

1. A load measuring device for a railcar bogie in which a first elastic body constituted by a vibrationproof rubber or a suspension spring is interposed between an axle box and a bogie frame, the load measuring device comprising:

a first load fluctuation sensor disposed in parallel with the first elastic body, the first load fluctuation sensor being configured to deform in conjunction with elastic deformation of the first elastic body in a first direction that is one of either (i) a vertical direction with respect to the railcar bogie, or (ii) a lateral direction with respect to the railcar bogie, the first elastic body supporting a downward load from the bogie frame, the first load fluctuation sensor being configured to vary an electric output based on changes in electrostatic capacitance of the first load fluctuation sensor resulting from the deformation of the first load fluctuation sensor in conjunction with the elastic deformation of the first elastic body in the first direction, the deformation of the first load fluctuation sensor is parallel and directly proportional to the deformation of the first elastic body.

2. The load measuring device according to claim 1 , wherein the first load fluctuation sensor includes:

a first electrode configured to move in the first direction in conjunction with a movement of a lower end of the first elastic body in the first direction;

a second electrode configured to move in the first direction in conjunction with a movement of an upper end of the first elastic body in the first direction; and

a first intermediate member sandwiched between the first electrode and the second electrode in the first direction, the first intermediate member being configured to deform by relative movements of the first electrode and the second electrode in the first direction, the deformation of the first intermediate member varying electric outputs of the first electrode and the second electrode.

3. The load measuring device according to claim 2 , wherein:

the first elastic body is the vibrationproof rubber;

the first electrode is configured to move in the first direction integrally with a lower member attached to a lower surface of the vibrationproof rubber; and

the second electrode is configured to move in the first direction integrally with an upper member attached to an upper surface of the vibrationproof rubber.

4. The load measuring device according to claim 1 , wherein the first load fluctuation sensor has a lower deformation resistance than the first elastic body.

5. The load measuring device according to claim 1 , wherein the first load fluctuation sensor is located outside of the first elastic body.

6. The load measuring device according to claim 1 , wherein:

the first elastic body is the vibrationproof rubber; and

the first load fluctuation sensor is surrounded by the first elastic body.

7. A load measuring device for a rail car bogie in which a first elastic body constituted by a vibrationproof rubber or a suspension spring is interposed between an axle box and a bogie frame, and a second elastic body constituted by a vibrationproof rubber or a suspension spring is interposed between the axle box and the bogie frame, the load measuring device comprising:

a first load fluctuation sensor disposed in parallel with the first elastic body, the first load fluctuation sensor being configured to deform in conjunction with elastic deformation of the first elastic body in a first direction that is one of either (i) a vertical direction with respect to the railcar bogie or (ii) a lateral direction with respect to the railcar bogie, the first elastic body supporting a downward load from the bogie frame, the first load fluctuation sensor being configured to vary an electric output based on the deformation of the first load fluctuation sensor in conjunction with the elastic deformation of the first elastic body in the first direction; and

a second load fluctuation sensor disposed in parallel with the second elastic body the second elastic body being configured to deform in conjunction with elastic deformation of the second elastic body in a second direction that is the other of (i) the vertical direction with respect to the railcar bogie, or (ii) the lateral direction with respect to the railcar bogie, the second elastic body supporting the downward load from the bogie frame, the second load fluctuation sensor being configured to vary an electric output based on the deformation of the second load fluctuation sensor in conjunction with the elastic deformation of the second elastic body in the second direction.

8. The load measuring device according to claim 7 , wherein the second load fluctuation sensor includes:

a third electrode configured to move in the second direction in conjunction with a movement of a lower end of the second elastic body in the second direction;

a fourth electrode configured to move in the second direction in conjunction with a movement of an upper end of the second elastic body in the second direction; and

a second intermediate member sandwiched between the third electrode and the fourth electrode in the second direction, the second intermediate member being configured to deform by relative movements of the third electrode and the fourth electrode in the second direction, the deformation of the second intermediate member varying electric outputs from the first electrode and the second electrode.

9. The load measuring device according to claim 7 , further comprising a processor configured to receive the electric output from the first load fluctuation sensor and the electric output from the second load fluctuation sensor, wherein:

based on a static wheel load input and an output relating to a vertical-direction load fluctuation from the first load fluctuation sensor or the second load fluctuation sensor while a railcar is traveling, the processor is configured to calculate a generated wheel load while the railcar is traveling; and

based on an output relating to a lateral-direction load fluctuation from the second load fluctuation sensor or the first load fluctuation sensor while the railcar is traveling, the processor is configured to calculate a generated lateral pressure of a wheel while the railcar is traveling.