PROBLEM TO BE SOLVED: To improve the visibility of a display image by avoiding a monitor display from being frequently switched even when a main speed change lever is operated in a repeating pattern such as "backward movement range → neutral range → backward movement range ...".SOLUTION: A control part 65 of a monitoring device includes: lever position discrimination means for discriminating in which range an operating position of a main speed change lever 53 is located, a forward movement range, a neutral range, or a backward movement range. When the main speed change lever is operated from the neutral range to the forward movement range, an image displayed on a monitor 57 is switched to an auger camera image. When the main speed change lever 53 is operated from the neutral range to the backward movement range, an image displayed on the monitor 57 is switched to a back camera image, and when the main speed change lever 53 is operated from the forward movement range or the backward movement range to the neutral range, an image displayed on the monitor 57 is not switched.COPYRIGHT: (C)2014,JPO&INPIT【課題】主変速レバーを「後進範囲→中立範囲→後進範囲・・・」のような繰り返しパターンで操作しても、モニタ表示が頻繁に切替わることを回避し、表示映像の視認性を向上させる。【解決手段】モニタ装置の制御部65は、主変速レバー53の操作位置が前進範囲、中立範囲、後進範囲のいずれにあるかを判別するレバー位置判別手段を備え、主変速レバー53が中立範囲から前進範囲に操作された場合は、モニタ57に表示する映像をオーガカメラ映像に切替え、主変速レバー53が中立範囲から後進範囲に操作された場合は、モニタ57に表示する映像をバックカメラ映像に切替え、主変速レバー53が前進範囲又は後進範囲から中立範囲に操作された場合は、モニタ57に表示する映像の切替えを行なわない。【選択図】図13
