Engine and transmission control system for combines and the like

A method of controlling a vehicle having an engine for driving both the ground wheels of the vehicle and at least one auxiliary mechanism, and a speed droop governor for regulating the fuel input to the engine in response to changes in the engine speed, said governor having a first speed droop characteristic, the engine being coupled to the ground wheels through a hydrostatic transmission and to the auxiliary mechanism through a power takeoff on the engine side of the transmission, said method comprising the steps of

• generating an electrical control signal that varies as a function of (1) a speed error signal which varies with changes in the difference between the actual speed of the engine and a reference speed for the engine, and (2) a droop factor having a second speed droop characteristic for controlling the setting of said transmission, and
• adjusting said hydrostatic transmission to regulate the ratio between the engine speed and the ground speed of said vehicle, thereby adjusting the load on said engine and the power transmitted to said ground wheels, in response to said electrical control signal, said droop factor in said control signal causing the resulting speed change effected by the adjustment of said transmission to follow a speed droop characteristic in which said first and second speed droop characteristics are factors.

In a crop-processing vehicle having an engine for driving both the ground wheels of the vehicle and a crop-processing mechanism, a speed droop governor having a first droop characteristic for regulating the fuel input to the engine in response to changes in the engine speed, the engine being coupled to the ground wheels through a hydrostatic transmission, and the power takeoff for the crop-harvesting mechanism being located on the engine side of the hydrostatic transmission, a control system comprising

• an actuator connected to said hydrostatic transmission for adjusting said transmission, thereby adjusting the load on said engine and the power transmitted to said ground wheels, in response to an electrical control signal, and
• means for generating said electrical control signal in response to variations in at least one parameter which varies with changes in the load on said engine, said control signal including a second droop characteristic in which said first droop characteristic is a factor so that said transmission adjustments vary the engine speed in inverse proportion to variations in engine load and by a smaller amount than the speed change that would otherwise be effected by the adjustment of said fuel input by said speed droop governor.

In a crop-processing vehicle having an engine for driving both the ground wheels of the vehicle and a crop-processing mechanism, the engine being coupled to the ground wheels through a hydrostatic transmission, and the power takeoff for the crop-processing mechanism being located on the engine side of the hydrostatic transmission, a control system comprising

• a speed droop governor having a first droop characteristic for adjusting the fuel input to said engine as a function of engine speed, said governor being designed to reduce the engine speed as the engine load increases, and
• a transmission control unit for adjusting said transmission as a function of at least one parameter that varies with engine load, to compensate for a substantial portion of the engine speed reductions that would otherwise be effected by said governor,
• said transmission control unit including means for generating a signal representing a droop factor, said signal controlling the adjustment of said transmission to reduce the engine speed only slightly as the engine load increases, with a modest reduction in the ground speed of the combine, so that the engine speed follows a second droop characteristic in which said first droop characteristic is a factor.