TRACK GP 1912720 - Caterpillar

When the blade tilt joystick is in the TILT LEFT position, joystick base control (22) sends a pulse width modulated signal through connector (21) to ECM (24).The ECM (24) interprets the signal as an operator request to tilt the blade left. As the blade tilt joystick is moved further to the left, the duty cycle percentage increases. In the TILT LEFT position, ECM (24) sends a signal of 0 amps through connector (18) to solenoid valve (32). As a result, solenoid valve (32) is not energized and solenoid valve (32) blocks the pilot oil from pilot oil supply passage (26) to passage (53). While pilot oil supply passage (26) is blocked, passage (53) is open to passage (54). Pilot oil in chamber (59) flows to passage (53). The oil flows from passage (53) through passage (54) to pilot oil return passage (13). Then, the oil flows from pilot oil return passage (13) back to the hydraulic tank.Also, ECM (24) sends a signal with a current between initiation current and saturation current through connector (19) to solenoid valve (33). The amount of current is proportional to the duty cycle received from the joystick. As a result, solenoid valve (33) becomes energized and solenoid valve (33) shifts downward . Solenoid valve (33) blocks the pilot oil from passage (44) to passage (43). While passage (43) is blocked, passage (44) is open to pilot oil supply passage (30). Oil flows from pilot oil supply passage (30) to passage (44). Oil flows from passage (44) to chamber (40) The amount of oil flowing from passage (44) to chamber (40) is proportional to the amount of current energizing the solenoid valve (33).Since the oil pressure in chamber (40) is greater than the pressure in chamber (59), the pressure in chamber (40) overcomes the combined force of spring (57) and of spring (58) and valve spool (20) shifts downward. Initially, as valve spool (20) shifts downward, a path opens from port (35) to load sensing passage (52). The pressure oil flows from port (35) to load sensing passage (52). The oil flows from load sensing passage (52) through orifice (51) of flow compensator spool (29). The pressure of the oil combines with the force of spring (48) in order to shift flow compensator spool (29) to the right. As flow compensator spool (29) shifts, port (46) opens to passage (31). The high-pressure oil in passage (31) flows through port (46) to passage (45). As spool (20) continues to shift downward, passage (47) opens to load sensing passage (52). The pressure of the blocked oil lowers and check valve (28) opens. High-pressure oil in passage (45) flows through check valve (28) to passage (47). Then, the oil flows from passage (47) to load sensing passage (52). Some of the oil in load sensing passage (52) flows to resolver (27) and the oil moves resolver (27) to the right. Oil is then sent through the rest of the resolver network through passage (49) to load sensing