Form No. 29704
XL 4200/XL 5200 HYDRAULIC SYSTEM OPERATIONS MANUAL
The swing pump is driven by the PTO drive of the main pump and turns at the same RPM as the engine. It has a
rotary piston group and gear-type charge pump.
See Figure 15, Figure 16, Figure 26 and Figure 27
Mechanical
power from the engine is changed to hydraulic power at the pump, then changed back to mechanical power
whenever the swing motor drives the pinion of the swing transmission. Swashplate angle in the pump determines the
direction and rate of fluid flow from the pump into the motor. The stroking piston in the pump case shifts the
swashplate via a guide pin. Springs are used to return the stroking piston to center. A stroke limiter sleeve controls
maximum swashplate angle. A tie rod assembly provides a guide for the stroking piston and is used to mechanically
center the pump.
See Figure 35
The swing pump is an overcenter, variable displacement, axial pump. The pump housing is a cast case that encases
the rotary group and swashplate, stroking pistons and driveshaft. A port block bolts to the pump case and contains
pump ports, high pressure reliefs, charge pump assembly and reliefs, suction port for the charge pump and a
through drive for the auxiliary pumps. A separate torque control valve bolts to the pump case. A hydraulic braking
valve bolts to the torque control valve body.
See Figure 15, Figure 16, Figure 26 and Figure 27
The charge pump and charge relief valve are required for swing circuit operation.
See Figure 15, Figure 16, Figure
26 and Figure 27
The charge pump relief valve is set at 400 PSI. It provides makeup hydraulic fluid for the loop
and control fluid to the torque control. During normal operation, some internal leakage exists in the pump and
motor. Charge fluid is bled into the low pressure side of the loop to replenish loop fluid that has been lost due to
normal internal leakage. The high pressure/anti cavitation reliefs in the port block will provide makeup fluid anytime
loop pressure drops below the charge relief setting. Charge circuit fluid is provided to the torque control valve to shift
the pump. Charge fluid going over relief is directed to the pump case to provide lubrication to the pump. The pump
case is always filled with fluid during operation (Case Fluid).
If the pump, motor, or loop are serviced or replaced the components and loop must be refilled with (lean hydraulic
fluid before startup. If this is not done, bearing life and piston socket life can be seriously reduced. Follow Start-up
Procedure shown in
Section VII, Main Hydraulic Pump.
These procedures must also be adhered to if a vacuum
has been applied to the hydraulic system.
At the opposite end of the loop from the swing motor is a bent axis fixed displacement motor. It consists of a case,
endcover, rotary group, port plate and driveshaft. It converts hydraulic energy into mechanical energy.
See Figure 28
The swing motor is attached to the swing parking brake and swing transmission. The parking brake is used to hold
the upperstructure stationary (when not swinging). It is strictly a static brake. It is not designed to stop the
upperstructure swing.
XI. Swing Circuit
(continued)
29
Содержание XL4000
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Страница 305: ...GRADALL h y d r a u l i c e x c a v a t o r s XL 4000 5000 CENTER PIN REBUILD Form No 20026 Part No 2460 4164 ...