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 retainer. The block spring 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 piston and spring. The servo piston
opposes the action of the bias piston and spring forcing the swashplate out of stroke.
The pump control, by varying the pressure at the servo piston, controls the displacement of fluid in the
system circuit.
Service Manual
D1 High Power Open Circuit Pumps Size 65/130/145/193/260
Introduction
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Danfoss | July 2019
L1527453 | AX00000292en-CN0201 | 7