Patent ID: 8636326

Claim:
A crawler type travel unit comprising: a rear axle case of a travel machine body; a track frame swingably supported by said rear axle case through a rocking shaft; a front driven wheel disposed on a front end portion of said track frame; a rear driven wheel disposed on a rear end portion of said track frame; three idling wheels aligned between said front driven wheel and said rear driven wheel at intervals in a longitudinal direction; a rear axle supported by said rear axle case; a drive wheel which is disposed upward of a longitudinal intermediate portion of said track frame and is configured to receive power transmitted from said rear axle; and a crawler belt wrapped around said drive wheel, said front driven wheel, said rear driven wheel and said idling wheels, wherein a horizontal distance during contact with the ground between a center of the rocking shaft and a center of a spindle of said front driven wheel is set longer than a horizontal distance between the center of the rocking shaft and a center of a spindle of said rear driven wheel, and said rocking shaft is disposed downward of a center of said drive wheel, so as to give an upward force to a front portion of said travel unit when tension is applied to said crawler belt; wherein said rocking shaft is disposed at a position immediately below a center of said drive wheel and displaced frontward from the position; wherein each of two idling wheels on a rear side of said three idling wheels is pivoted on a first rocking link, and a longitudinal intermediate portion of said first rocking link is pivoted on said track frame through a first pivot shaft; wherein a horizontal distance between said center of said rocking shaft and said center of the first pivot shaft is set shorter than a horizontal distance between said center of said rocking shaft and a wheel shaft of the idling wheel on a front side, and a wheel shaft of a forward one of the two rear idling wheels pivoted on the first rocking link is arranged forwardly of the rocking shaft, so as to support a load acting on the track frame by the two rear idling wheels; wherein, as seen in vertical section from behind, the track frame has an upper section with a larger right/left width and a lower section with a smaller right/left width; and wherein the idler wheels extend across a right/left width of the track frame so that the idler wheels are located on lateral sides of the smaller-width lower section and directly below lateral sides of the larger-width upper section.