CAP 0952006 - Caterpillar

Charge Pump
Illustration 6 g00489192
Charge pumpThe charge pump fills the system with oil during start-up. The pump provides cooled filtered oil for the steering pilot circuit and the pump provides oil in order to compensate for the internal leakage inside the closed circuit system. The charge pressure and the pressure in the closed loop is limited to 2500 300 kPa (365 45 psi). The pressure is limited by the charge pressure relief valve. The charge pump is a crescent type gear pump. The charge pump is a component of the steering pump that is mounted on the rear of the steering pump.Pump Control Valve
Illustration 7 g00489194
Pump control valve (1) Spring (2) Spool (3) Lever (4) Spring (5) Lever (6) Pin (7) Spring (8) Passage for charge oil (9) Passage for control piston (10) Feedback lever (11) Passage to control piston (12) Passage for charge oilThe pilot valve sends pilot oil at a controlled pressure from 600 to 1800 kPa (88 to 260 psi). The pressure is dependent on the movement of the steering tiller. The pump output is proportional from 0 to 100 percent. The output is based on the pilot pressure.The oil from the pilot valve is directed to either the right end or the left end of spool (2). The pressure shifts the spool and the spool sends the charge pressure oil to the control piston. As the spool shifts, pin (6) moves either lever (3) or lever (5). The pin compresses spring (4). The spring resists the movement of spool (2) .Charge pump oil is sent to the control piston. As the control piston is moved to upstroke the pump, feedback lever (12) is also moved. Feedback lever (12) moves either lever (3) or lever (5). The lever that is moved is the opposite of the lever that is moved by spool (2). Spring (4) compresses further. The force of spring (4) pulls the lever that was moved by spool (2), back toward the NEUTRAL position. Also, the spring moves spool (2) toward the NEUTRAL position. When the spool is in the correct position, the movement of spool (2) stops. The spool meters the charge oil to the control piston. The control piston maintains the required swashplate angle.Pump Control Piston
Illustration 8 g00489196
Pump control piston (1) Springs (2) Slot (3) Control piston (4) SlotOil from the pump control valve flows to either the right end or the left end of control piston (3). The oil pressure moves the control piston in order to upstroke the pump.One end of a lever that is attached to the swashplate is in slot (2) in the control piston. When the control piston moves, the lever moves the swashplate. The swashplate moves to the angle that corresponds to the position of the control piston.The feedback lever to the pump control valve is in slot (4). The feedback lever works with the pump control valve in order to maintain precise control of the pump displacement.When the control pressure is relieved, springs (1) return the