HOUSING GP-FRONT 4328266 - Caterpillar

Illustration 2 g00868659
Schematic for 3161 Governor (typical example)
Operation of the 3161 Governor
The 3161 Governor uses engine lubrication oil for the hydraulic system. The pressurized engine oil supply is sent to the governor oil reservoir through an orifice which can be removed from the governor housing for cleaning. First, the oil will travel through internal passages to the suction side of the gerotor pump. The oil will then travel to the pressure side of the gerotor pump as the drive shaft is turned by the engine. An accumulator spring and a piston will keep the pump pressure at approximately 690 kPa (100 psi). The accumulator piston moves upward in the piston cylinder until the pump pressure is 690 kPa (100 psi). The ports in the piston will open in order to control the pump pressure, after the established pump pressure is reached.The pump pressure, which is set by the accumulator, controls the work output of the governor.Increase In Speed Setting
When the speed setting shaft is turned clockwise, the speed setting of the governor is increased. The high idle screw limits the high speed setting of the governor. As the speed setting shaft turns, the speed setting lever pushes down on the floating lever which is fastened to the speeder plug. The downward pressure on the speeder plug puts the speeder spring under compression. The force of the speeder spring will then become greater than the centrifugal force of the ballhead flyweights. The ballhead pilot valve plunger will move down. The governor speed setting is then increased.When the pilot valve plunger is moved down the pressurized engine oil will move under the power piston. This process will push the piston upward. This will move the terminal lever upward. Turn the output shafts toward the increased fuel position in order to increase engine speed.Before the engine reaches the new set speed, the compensation system will return the pilot valve plunger back to the center position. This will put the governor under stable control.The oil above the power piston is connected to the upper side of the buffer piston and lower side of the pilot valve compensation land. As the power piston moves upward, the oil pressure will push the buffer piston downward. This will increase the compression of the lower buffer piston spring. The force of the spring works against the buffer piston movement and this results in a small increase in oil pressure on the upper side of the buffer piston. The increased pressure is directed to the lower side of the pilot valve compensation land. This will force the pilot valve plunger up to the center position. This stops the flow of pressurized engine oil to the lower side of the power piston and movement of the piston is stopped.As the pilot valve plunger is returned to the center position and the power piston movement is stopped, there is oil leakage through the needle valve orifice. This will allow the oil pressure above the pilot valve compensation land and the