Seal structure of crawler-driving apparatus

A seal structure of a crawler-driving apparatus, arranged between a rotational casing that drives a crawler of a crawler vehicle and a fixed housing fixed to a vehicle body of the crawler vehicle, comprising:

• a first holding groove in an annular shape, the first holding groove being formed in one of the rotational casing and the fixed housing;
• a second holding groove in an annular shape, the second holding groove being formed in another one of the rotational casing and the fixed housing to face the first holding groove;
• a seal ring held in the first holding groove;
• a slide ring that is held in the second holding groove and has a higher rigidity than that of the seal ring;
• a first elastic member held in the first holding groove to bias the seal ring towards the slide ring;
• and
• a second elastic member held in the second holding groove to bias the slide ring towards the seal ring,
• wherein,
• one of the seal ring and the slide ring has an annular guide protrusion protruding to another one of the seal ring and the slide ring,
• an annular guide trench that makes sliding contact with the guide protrusion is formed in the other one of the seal ring and the slide ring,
• the first holding groove has a first outer circumferential groove side surface and a first inner circumferential groove side surface extending in a direction of the rotation axis of the rotational casing,
• the second holding groove has a second outer circumferential groove side surface and a second inner circumferential groove side surface extending in the direction of the rotation axis of the rotational casing,
• the slide ring contacts both the first outer circumferential groove side surface and the first inner circumferential groove side surface of the first holding groove, and
• the slide ring contacts both the second outer circumferential groove side surface and the second inner circumferential groove side surface of the second holding groove.