CAMSHAFT GP-SGL 10R7155 - Caterpillar

Pump Servovalve
(1) Servovalve. (11) Pressure compensator spool. (12) Spring. (13) Adjustment screw. (14) Passage (from pump outlet opening). (15) Passage (to hydraulic system). (16) Oil Drain passage. (17) Flow compensator spool. (18) Sensor oil line connection.With pressure compensator spool (11) moved, the oil in passage (14) now goes through passage (15) to control piston (2) in the hydraulic pump. The force of the oil from passage (15) moves control piston (2) and the piston moves swashplate (4) to its minimum angle position (approximately 0° angle). When drive shaft (5) and barrel (10) turn, with swashplate (4) at the minimum angle position, pistons (9) get very little movement in and out of barrel (10) as the retraction plate and slippers follow the approximate 0° angle of the swashplate. The very little movement of pistons (9) is enough to keep the pressure of the oil, from pump outlet opening (8), at the pressure setting of the servovalve. The oil from the pistons that cannot go through outlet opening (8) does go into the pump body for pump lubrication. The oil in the pump body goes through pump drain line (22) to the hydraulic tank.When either the control lever held in the position to operate the stopped cylinder is released, or if whatever stopped the operation of the cylinder is removed the pressure of the oil in the hydraulic system decreases. With the decrease in oil pressure spring (12) moves pressure compensator spool (11) in servovalve (1). Now, there is no pressure oil in passage (15) to control piston (2) in the pump. With no pressure oil to control piston (2), spring (3) moves swashplate (4) to its maximum angle position and the liter/min (gpm) pump output is again at the maximum.The action of swashplate (4), from the minimum angle to the maximum angle position and pistons (9) to increase their strokes for maximum pump output is very fast (approximately 10 milliseconds).The pressure setting of servovalve (1) can be adjusted, if necessary. Turn adjustment screw (13) clockwise for an increase or counterclockwise for a decrease in the pressure setting of the servovalve.
Hydraulic Pump Oil Lines
(7) Pump inlet (from the tank). (8) Pump outlet (to the hydraulic system). (18) Sensor oil line connection. (19) Check valve (orifice). (20) Lever (forward for bulldozer operation). (21) Sensor oil line. (22) Pump drain line to hydraulic tank.The variable low liter/min (gpm) output from the hydraulic pump is when the pump control is IN for the BULLDOZER position. The pump control moves lever (20), on check valve (19), forward and this puts an orifice in the check valve.With the pump control in the BULLDOZER position, and there is no bulldozer hydraulic cylinder operation, the orifice in check valve (19) increases the oil pressure of the pump oil between pump outlet (8) and check valve (19) to 1380 kPa (200 psi). The oil in pump outlet (8) is also in passage (14) in pump servovalve (1). The 1380 kPa (200 psi) pressure of the oil in passage