Automatic transmission system for bulldozer

摘要

An automatic transmission system for a bulldozer includes an automatic speed stage shifting section that switches among speed stages depending on a vehicle speed, a speed stage maintaining section that maintains a currently selected speed stage until a predetermined speed stage shifting disobedient time elapses after completion of a speed stage shifting while disobeying a switching instruction from the automatic speed stage shifting section, a load detecting section that detects a vehicle load, and a control restricting section that restricts a control processing of the maintaining section for causing it to obey the shifting section's instruction when the vehicle load is a predetermined load or greater even before the disobedient time elapses.

主权项

1. An automatic transmission system for a bulldozer including a transmission having a plurality of speed stages, the speed stages including at least a first speed stage that is a lowest speed stage among the speed stages, the automatic transmission system comprising:
an automatic speed stage shifting section configured to switch among the speed stages in accordance with a vehicle speed; a speed stage maintaining section configured to execute a control processing to maintain a currently selected speed stage until a predetermined speed stage shifting disobedient time elapses after completion of a speed stage shifting, the control processing being configured to cause a switching instruction from the automatic speed stage shifting section to be disobeyed; a load detecting section configured to detect a load applied to the bulldozer; and a control restricting section configured to restrict the control processing of the speed stage maintaining section upon the load detected by the load detecting section being greater than or equal to a predetermined load such that the switching instruction is obeyed even before the speed stage shifting disobedient time elapses, the control restricting section being configured to restrict the control processing of the speed stage maintaining section only either when the bulldozer starts moving while a speed stage other than the first speed stage is selected, or when a travel direction of the bulldozer is switched between a forward travel direction and a rearward travel direction while a speed stage other than the first speed stage is selected.