Hydraulic Controls; Hydraulic Proportional Control; Hydraulic Two-Position Control - Danfoss H1 Series Technical Information

Technical Information
H1 Bent Axis Variable Displacement Motors, Size 060/080/110/160/210/250
Control operation and description

Hydraulic controls

Hydraulic proportional control

Hydraulic two-position control

38 | © Danfoss | December 2016
Motor displacement can be changed hydraulically, under load, from maximum to minimum
displacement and vice versa in response to an external hydraulic signal.
The hydraulic proportional control consists of a proportional hydraulic actuator which acts directly on a
two-position, three-way porting spool. It uses an external source for control pressure supply. When
pressurizing, the hydraulic actuator pushes the spool which then ports high pressure to the larger
diameter of the servo piston. The servo piston and rotating group move to change the displacement to
the point where the pressures on the servo are in balance with the force from the feedback spring.
De-energized = maximum displacement
With a de-energized (not pressurized) to maximum displacement control, the de-energized proportional
valve keeps the motor at maximum displacement.
When energized, the hydraulic actuator pushes on the porting spool which moves to port high system
pressure to the larger diameter end of the servo piston.
Depending on the pressure level supplied to the proportional actuator, the motor will stroke between
maximum displacement at start pressure setting and minimum displacement at maximum pressure
setting.
De-energized = minimum displacement
With a de-energized (not pressurized) to minimum displacement control, the de-energized proportional
valve keeps the motor at minimum displacement.
When energized, the hydraulic actuator pushes on the porting spool which moves to port high system
pressure to the larger diameter end of the servo piston.
Depending on the pressure level supplied to the proportional valve, the motor will stroke between
minimum displacement at start pressure setting and maximum displacement at maximum spressure
setting.
The hydraulic two-position control uses an external source for control pressure supply (e. g. charge
pressure). This control pressure acts on a two position, three-way porting spool. Servo pressure is
internally supplied to the two-position porting spool by an integral system shuttle check valve.
Default (without control pressure) = maximum displacement
With no control pressure applied, the motor operates at maximum displacement.
When control pressure is applied, the spool shifts, porting high system pressure to the large diameter end
of the servo piston, shifting the motor to minimum displacement.
When the control pressure is removed, spring forces move the spool, allowing the large diameter end of
the servo piston to drain to tank, shifting the motor to maximum displacement.
Default (without control pressure) = minimum displacement
With no control pressure applied, the motor operates at minimum displacement.
When control pressure is applied, the spool shifts, porting the large diameter end of the servo piston to
tank, shifting the motor to maximum displacement.
When the control pressure is removed, spring forces move the spool, porting high pressure to the large
diameter end of the servo piston, shifting the motor to minimum displacement.
11037153 | BC00000043en-US1103