Symbols used in Danfoss literature
WARNING may result in injury
Tip, helpful suggestion
CAUTION may result in damage to product or
property
Lubricate with hydraulic fluid
Reusable part
Apply grease / petroleum jelly
Non-reusable part, use a new part
Apply locking compound
Non-removable item
Inspect for wear or damage
Option - either part may exist
Clean area or part
Superseded - parts are not interchangeable
Be careful not to scratch or damage
Measurement required
Note correct orientation
Flatness specification
Mark orientation for reinstallation
Parallelism specification
Torque specification
External hex head
Press in - press fit
Internal hex head
Pull out with tool – press fit
Torx head
Cover splines with installation sleeve
O-ring boss port
Pressure measurement/gauge location or
specification
The symbols above appear in the illustrations and text of this manual. They are intended to communicate
helpful information at the point where it is most useful to the reader. In most instances, the appearance
of the symbol itself denotes its meaning. The legend above defines each symbol and explains its purpose.
Design
Danfoss H1 closed circuit piston pumps convert input torque into hydraulic power. The input shaft
transmits rotational force to the cylinder block. Bearings at the front and rear of the pump support the
shaft. Splines connect the shaft to 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 block spring, ball guide,
and slipper retainer hold the slippers to the swashplate. 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 low pressure and the other half to high pressure. As each piston cycles
in and out of its bore, fluid is replenished by charge flow and displaced to the outlet thereby imparting
hydraulic power into the system. A small amount of fluid is allowed to flow from the cylinder block/valve
plate and slipper/swashplate interfaces for lubrication and cooling. Case drain ports return this fluid to
the reservoir.
The angle of the swashplate controls the volume and direction of fluid displaced into the system. The
servo piston controls the angle of the swashplate. The pump control, by varying the pressure at the servo
piston, controls the piston’s position. An electric signal to the control coils transmits the command from
the operator to the pump. Mechanical feedback of the swashplate position to the control through the
feedback pins allows for very precise displacement control and increases overall system stability. Non-
feedback control options do not use the mechanical feedback link.
Service Manual
H1 Pumps 069/078, 089/100, 115/130, 147/165, 210/250
Introduction
©
Danfoss | May 2018
520L0848 | AX00000087en-US0308 | 7