Development of High Reliability and Low Cost Electronic Governor System for Small Diesel Engine for Agricultural and Industrial Use 2001-01-1866

The latest frequency-conversion system, as typified by inverter power generator, is capable of providing superb fuel economy and NVH characteristics by means of real-time control of the engine speed according to its load condition. The current mechanical governor, however, can difficultly achieve that demand of performance. In order to meet these requirements, we have developed the electronic governor system having high control flexibility and response for small diesel engines for agricultural and industrial use.

In developing this electronic governor system, we have adopted a method that can minimize modification of current engines. We have successfully developed the electronic governor system by means of a post-assembly installation, in which dedicated functional devices are installed to complete engine while keeping intact the current highly reliable PFR type fuel-injection pump and the mechanical governor. This method allows the electronic governor to control engine speed within the limit of fuel-delivery quantity regulated by the mechanical governor. It means that the full load fuel-delivery characteristic curve is unaffected by the installation of the electronic governor, and that the emission performance attained with the mechanical governor is also unchanged.

In order to perfect this post-assembly installation method, we have newly developed the actuator having compatibility with the current engine stop solenoid, as well as the injection quantity sensor having compatibility with start spring assembly. These functional devices have high reliability adaptable to harsh operational environment typical of agricultural and industrial engine applications. We have combined these devices with the Electronic Control Unit (ECU), which has the reliability well proven in our current in-house production, in order to cope with diverse applications of these engines.

This electronic governor system offers the choice of two types according to the performance requirements of equipment. One is the basic type electronic governor system that has no injection quantity sensor and operates only in the isochronous mode that works to keep the constant engine speed. Another is the high precision type electronic governor system that can operate not only in the isochronous mode but also in the droop mode, the characteristics of mechanical governor, and in the inverse-droop mode that increases engine speed to make the torque follow the load fluctuations at low speed range.