Cub Cadet Domestic Series 7000 Service Manual page 9

2.4. The lower part of the pump contains a fixed dis-
placement axial piston hydraulic motor. The
motor is driven by the output of the variable dis-
placement pump.
2.5. The hydro. control arm (scissors bracket) moves
a swash plate that controls the output of the
pump: tilting the swash plate in one way causes
the variable displacement pump to drive fluid
through the fixed displacement pump in one
direction. See Figure 2.5.
Variable displacement pump
Fixed displacement
motor
Motor block
Figure 2.5
NOTE: In figure 2.5, the pistons in the variable
displacement pump are alternately pressed into
the bores, and then released from bores of the
rotating pump block by the tilt of the swashplate.
• On the right side of the pump block in figure 2.5,
the pistons are down.
• The pistons are extended on the left side of the
pump block. They are forced up by springs con-
tained in the pistons.
• This action causes the pistons to pump fluid in
one direction.
• The further the swash plate is tilted, the greater
the movement of the pistons as the pump block
rotates.
• As the travel of the pistons is increased, the dis-
placement of the pump is increased, and more
fluid is pumped.
• The more fluid is pumped, the faster the fixed
displacement motor is driven.
2.6.
Input shaft
Swash
plate
Pump
block
2.7.
Swash plate
angle
2.8.
2.9.
•
•
•
•
2.10. If the hydrostatic drive is not performing cor-
5
Domestic Series 7000 Hydraulics
Tilting the swash plate the other way causes the
variable displacement pump to drive fluid
through the fixed displacement pump in the
opposite direction. See Figure 2.6.
Fixed displacement
motor
Pistons
Figure 2.6
When the swash plate is flat, the pump pistons
do not move up and down, no fluid is displaced
and no power is transmitted to the fixed dis-
placement pump.
The charge pump maintains a supply of pressur-
ized fluid to the variable displacment pump to
feed and lubricate the pump.
The charge check valves direct the flow of pres-
surized fluid to the ports that feed the pistons of
the variable displacement pump.
When driving forward, fluid flows into the
varaible displacment pump thorugh one set of
ports, and out through a second set.
When driving backwards, the flow is reversed.
One check valve opens and the other one
closes, depending on the direction of fluid flow.
If the hydro. is in "neutral", lubrication is provided
to ths spinning (but not pumping) pump and
motor blocks through separate channels in the
housing.
rectly, begin diagnosing with simple things that
can bee seen with minimal disassembly.
Swash plate
angle
Pistons