TURBOCHARGER GP 2071352 - Caterpillar

Illustration 5 g00676266
Relief valve (7) Passage (13) Passage (22) Valve (23) Spring (24) Passage (25) Liner (26) Piston (27) Piston chamberRelief valves (2) and (8) are located in the top of swing motor (5). These relief valves limit the pressure in the swing circuit to the relief setting. This provides a cushion effect at a start or stop of the swing operation. When the swing stops, oil supply to the swing motor is insufficient. In this case, the return oil from control valve (16) is supplied to the swing motor as makeup oil. This makeup oil prevents a vacuum from being generated. When the swing control lever is moved back to the NEUTRAL position from the SWING RIGHT position, both the inlet port and the outlet port of the swing control valve are closed. Oil flow is now blocked at ports (11) and (14). The mass (weight and size) of the upper structure causes the swing motor to rotate for a short time after the swing control lever is moved back to the NEUTRAL position. The oil flow from rotary group (6) is blocked at port (14). Therefore, the pressure of the oil in passage (7) increases. The increased pressure oil in passage (7) forces valve (22) to the right (open position) against the force of spring (23) in relief valve (8). Oil now flows through passage (13) and check valve (3) to passage (1). From passage (1), oil enters motor rotary group (6), and the oil is absorbed there. Thus, the energy of the rotating upper structure is absorbed at the stop of the swing movement.The oil in passage (7) goes through passage (24) of valve (22) to piston chamber (27). Because the force of spring (23) is less than the relief valve pressure setting, valve (22) opens just before the oil pressure in passage (7) reaches the relief pressure setting. This allows the oil to vent. At the same time, the pressure oil in piston chamber (27) moves piston (26) to the left against the force of spring (23). For approximately 0.1 second of this piston movement, the oil pressure in piston chamber (27) is lower than the relief pressure setting. When the left end face of piston (26) comes in contact with liner (25), the oil pressure in passage (7) increases to the relief pressure setting. All oil flow is discharged from valve (22) to passage (13) .The pressure increases gradually from the cracking of valve (22) until piston (26) comes into contact with liner (25). Therefore, the peak pressure is not attained. This two-stage relief action reduces the shock load when the swing motor stops. After the start