The governor control is linked to the lever on the engine governor. The operation of the governor controls the amount of fuel necessary for the engine to maintain the selected engine rpm even when the load changes.
The hydra-mechanical governor has engine driven governor weights (12), governor spring (5), a hydraulic valve (13) and piston (14). The valve and piston are connected to rack (17) in the fuel injection pump housing. The engine lubricating oil pump supplies pressure oil through passage (16) and around sleeve (15) for the hydraulic operation of the governor. The accelerator pedal controls only the compression of governor spring (5). The compressed spring force always pushes to increase the supply of fuel to the engine while the centrifugal force of the engine driven governor weights are always pulling to decrease fuel to the engine. The governed rpm of the engine is when these two forces balance.
HYDRA-MECHANICAL GOVERNOR (Typical Example)
1. Collar. 2. Speed limiter plunger. 3. Lever assembly. 4. Seat. 5. Governor spring. 6. Thrust bearing. 7. Oil passage. 8. Drive gear (weight assembly). 9. Cylinder. 10. Bolt. 11. Spring seat. 12. Weights. 13. Valve. 14. Piston. 15. Sleeve. 16. Oil passage. 17. Fuel rack. The governor valve is shown in the position when the force of the weights and the force of the spring are balanced.
When engine load increases, engine rpm decreases and revolving weights (12) slow down. The weights move toward each other and allow governor spring (5) to move valve (13) forward. As valve (13) moves, an oil passage around valve (13) opens to pressure oil. Oil then flows through passage (7) and fills the chamber behind piston (14). The pressure forces the piston and rack forward, increasing the amount of fuel to the engine. Engine rpm increases until the revolving weights rotate fast enough to balance the force of the governor spring.
When engine load decreases, engine rpm increases, revolving weights (12) speed-up, and the toes on the weights move valve (13) rearward, allowing the oil behind piston (14) to flow through a drain passage opened at the rear of the piston. At the same time, the pressure oil between sleeve (15) and piston (14) forces the piston and rack rearward, decreasing the amount of fuel to the engine. Engine rpm decreases until the revolving weights balance the force of the governor spring.
When the engine is started, speed limiter plunger (2) restricts the movement of the governor control linkage. When operating oil pressure is reached, the plunger in the speed limiter retracts and the governor control can be moved to the HIGH IDLE position.
When the engine rpm is at LOW IDLE, a spring-loaded plunger within the lever assembly in the governor bears against the shoulder of the low idle adjusting screw. To stop the engine, the plunger must be forced past the shoulder on the adjusting screw.
Oil from the engine lubricating system lubricates the governor weight bearing. The various other parts are splash lubricated. The oil from the governor drains into the fuel injection pump housing.