Roller device and roller shell for track-type work vehicle

A roller device for a track-type work vehicle, comprising:

• a shaft including a rotation axis;
• a bushing including a small-diameter part arranged at an end, and a large-diameter part arranged to have a step part with the small-diameter part and having an outer circumferential surface with a recess, the bushing being fitted to an outer circumference of the shaft so as to be rotatable about the rotation axis relative to the shaft;
• a roller shell including a first cylindrical part having a first outer circumferential surface and a first inner circumferential surface, and a second cylindrical part having a second outer circumferential surface and a second inner circumferential surface, an outer diameter of the first cylindrical part being larger than an outer diameter of the second cylindrical part, an inner diameter of the first cylindrical part being smaller than an inner diameter of the second cylindrical part, the first cylindrical part being fitted at the first inner circumferential surface to the small-diameter part of the bushing, the second cylindrical part being fitted at the second inner circumferential surface to the large-diameter part of the bushing, the second cylindrical part having at the second inner circumferential surface a groove part which is open at an end surface of the second cylindrical part in an extending direction of the rotation axis, the roller shell engaging with the step part;
• an engaging member fitted to the recess and engaging with the groove part;
• and
• a retainer formed to be annular and detachably attached to the bushing to hold an end surface of the roller shell.