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DiReCt DisPLaCement
ContRoL (DDC) m25,
m35/44 vaRiabLe
PumPs
Series 40 Axial Piston Pumps
Technical Information
Control options
The Direct Displacement Control (DDC) can be located on either side of a Series 40
- M25, M35, or M44 pump. It provides a simple, positive method of control. Movement
of the control shaft causes a proportional swashplate movement, thus varying the
pump's displacement from full displacement in one direction to full displacement in the
opposite direction.
Some applications (generally vehicle propel) require a provision for non-linear control
input to reduce control sensitivity near neutral. Damping or frictional forces may be
necessary to produce desirable control feel.
Neutral position is not factory set, nor is there any internal neutral return mechanism.The
application must include provisions for all control linkage and neutral return fuctionality.
With no external forces applied to the swashplate trunnion, internal hydraulic forces may
not return the swashplate to the neutral position under all conditions of operation.
The DDC is available on variable pumps and tandem pumps.
external control handle requirements
Maximum allowable trunnion torque is 79.1 N•m [700 in•lbf ] for M25, M35, and M44.
Minimum torque necessary to hold the swashplate at a zero angle for neutral is 2.3 N•m
[20 in•lbf ]. Maximum trunnion angle is 15° for M25 and 16° for M35 and M44.
DDC on Left Side of M35 Pump
Trunnion
DDC input specs
Max torque
Nm [in·lbf ]
Min torque
Nm [in·lbf ]
Max angle
M25: 15°
Pump flow direction
Input shaft rotation
Trunnion location
Trunnion rotation
Port A Flow
PV or front PV
Fort B Flow
Port C (A) Fow
Rear PT
Port D (B) Flow
520L0635 • Rev EH • June 2009
Pump Displacement vs Swashplate Rotation
106 258
79.1
[700]
2.3
[20]
M35/44: 16°
CW
Right
Left
CW
CCW
CW
Out
In
In
In
Out
Out
In
Out
Out
Out
In
In
CW
Trunnion rotation
CCW
Trunnion rotation
100%
CCW
Right
Left
CCW
CW
CCW
CW
Out
In
Out
Out
In
Out
In
In
In
Out
In
In
Out
In
Out
Out
100%
T101 306E
CCW
In
Out
Out
In
41
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