3-16
3
TRAVEL MOTOR
FUNCTION
TRAVEL MOTOR
Hydraulic motor
The cylinder block (1) is constructed with the pistons (2),
and its end surface comes in contact with the valve plate
(3) containing two half-moon-shaped ports (B) and (C). The
cylinder block (1) rotates freely and is connected to the
shaft (4) via the splines. On the other hand, the swash plate
(5) is fixed to the housing.
When the high-pressure oil is directed to the port B, the
pistons (2) push the swash plate (5) with the force F per
piston.
F = P x A P: Pr
essure A: Piston sectional area
The force F used to push the swash plate (5) by the pistons
(2) is divided into two: the force F1 that pushes the plate
and the force F2 that rotates the cylinder block (1).
A rotational force is generated in the cylinder block (1) by
the total sum of the rotational forces in the high-pressure
side piston, and via the splines the torque is transmitted to
the shaft (4) to turn it. On the other hand, if the high-pres-
sur
e oil is directed to the port C, the rotation is the reverse
of the above.
Counter balance valve
When the high pressure oil is directed into the port P1, the
oil pushes up the check valve (6), flows into both the motor
port M1 and the chamber B in the pilot section. The pres-
sur
e oil flows into the motor from the motor port M1. On the
other hand, the return oil from the motor does not flow into
the port P2, because the passage between the motor port
M2 and the port P2 is blocked by the check valve (6). This
increases the pressure in the port P1 and the chamber B.
When the pressure in the chamber B becomes higher than
the set value for the spring (7), the spool (8) is moved to the
left so that the motor port M2 is connected with the port
P2. As a result, the motor starts running.
If the motor becomes too fast and the volume of oil flowing
out of the motor port M2 becomes larger than that of flow-
ing
into the motor port M1, the pressure in the port P1 and
the chamber B drops. When the pressure in the chamber
B becomes lower than the set pressure value, the spool
(8) returns to the right. As a result, the flow of the return oil
is narrowed down at the section D to generate the back
pressure in the motor port M2 and to slow down the motor
speed. If the motor speed becomes slower, the pressure
in the port P1 and the chamber B is increased again to
cause the spool (8) to move to the left. The back pressure
generated in the motor port M2 is eliminated. In this way,
the motor is controlled to run at the speed proportional to
the oil flow entered.
3MAA01Z
B
F
F
F
F2
F2
F2
F
F1
F2
D
C
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