Drive system control device for working vehicle
In a working vehicle, it is possible to achieve a downsizing of an engine by securing an output torque in a low rotating region of the engine without using any supercharger. In the working vehicle having the engine mounted to a travel machine body, a common rail type fuel injection device which injects fuel to the engine, and a continuously variable transmission which shifts power from the engine, a rotating speed N of the engine is limited to two kinds, N#1 and N#2. Further, a change gear ratio of the continuously variable transmission is changed and regulated in such a manner as not to change a vehicle speed of the travel machine body before and after changing the rotation speed N whichever of the two kinds N#1 and N#2 the rotating speed N of the engine is changed to.
1. A drive control system for a work vehicle, the work vehicle comprising an engine which is mounted to a travel machine body, the engine having a common rail type fuel injection device which injects fuel to the engine, the drive control system comprising:
a continuously variable transmission shifting power from the engine;
an engine speed sensor that detects a rotating speed of the engine;
a vehicle speed sensor that detects a vehicle speed of the travel machine body; and
an engine control unit configured to limit said rotating speed of the engine to two kinds of speed, namely a low speed and a high speed;
wherein when an engine load exceeds a first prescribed value while the rotating speed is limited to said low speed, the engine control unit is configured to adjust fuel consumption through the common rail type fuel injection device by changing said rotating speed to said high speed while controlling variation of a change gear ratio of said continuously variable transmission so that said vehicle speed is unchanged for a first time period spanning before, during, and after said changing said rotating speed from said low speed to said high speed; and
wherein when said engine load is less than a second prescribed value while the rotating speed is limited to said high speed, the engine control unit is configured to adjust fuel consumption through the common rail type fuel injection device by changing said rotating speed to said low speed while controlling variation of the change gear ratio of said continuously variable transmission so that said vehicle speed is unchanged for a second time period spanning before, during, and after said changing said rotating speed from said high speed to said low speed.