General Description - Danfoss 45 J Series Service Manual

Service Manual
Introduction (continued)

General Description

Series 45 J Frame Open Circuit Axial Piston Pumps
Danfoss Series 45 J frame open circuit piston pumps convert input torque into hydraulic power.
Rotational force is transmitted through the input shaft to the cylinder block. The input shaft is
supported by tapered roller bearings at the front and rear of the pump and is splined into the cylinder
block . A lip-seal at the front end of the pump prevents leakage where the shaft exits the pump
housing. The spinning cylinder block contains nine reciprocating pistons. Each piston has a brass
slipper connected at one end by a ball joint. The slippers are held to the swashplate by the spring
retainer and block spring. The block spring also holds the cylinder block to the valve plate. The
reciprocating movement of the pistons occurs as the slippers slide against the inclined swashplate
during rotation. Via the valve plate, one half of the cylinder block is connected to pump inlet and the
other half to pump outlet. As each piston cycles in and out of its bore, fluid is drawn from the inlet
and displaced to the outlet thereby imparting power into the system circuit. A small amount of fluid is
allowed to "leak" from the cylinder block/valve plate and slipper/swashplate interfaces for lubrication
and cooling. Case drain ports are provided to return this fluid to the reservoir.
The volume of fluid displaced into the system circuit is controlled by the angle of the swashplate. The
swashplate is forced into an inclined position (into stroke) by the bias spring. The servo piston
opposes the action of the bias spring forcing the swashplate out of stroke when hydraulic pressure in
the control circuit rises above the spring force.
The pump control, by varying the pressure at the servo piston, controls the displacement of fluid in
the system circuit. Controls designed for Pressure Compensation (PC) or Load Sensing (LS) are
available. For a detailed description of control operation, refer to
Pump and control sectional view
PC spool
Valve plate
Block
spring
Tapered
roller
bearing
Cylinder block
520L0607 • Rev AI • Sep 2013
LS control
(attached to endcap)
LS spool
Bias spring
Servo piston
Piston
Slipper retainer
operation, page 12.
Control options,
LS adjustment
PC adjustment
Slipper
Shaft seal
Input shaft
Tapered
roller
bearing
Swashplate
P104 362
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