Daewoo Solar 420LC-V, Manual

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S0707365
Page 6 Travel Motor (With Gearbox) (A6V160HD)
B. When Stopping by Deceleration.
If the pressure oil supplied by the port A is cut off during drive. there will be no hydraulic force.
Then, the spool (126) returns to the right (neutral position) through the stopper (125) by the
spring (128).
The hydraulic oil in chamber b goes through passage a into port A, and back pressure, which is
generated by throttling of passage a controls the return speed of spool (126).
At the same time, the hydraulic motor rotates by inertia force even without the pressure oil.
So the return oil from port D returns to port B through a gap between the spool hole and the rear
flange.
If the spool returns to the neutral position, hydraulic motor stops because all passages are
closed completely.
Like this, the spool’s returning speed controls the return oil from motor gradually according to
the spool’s shape, and stops the hydraulic motor.
As the hydraulic motor rotates because of inertia force, it tries to absorb the hydraulic oil. But
hydraulic oil cannot be supplied because the oil is blocked. So the hydraulic motor will be
damaged by cavitation. But, at the same time, the pressure at port D rises because the return
oil from the hydraulic motor is closed.
By this pressure, the spool (137) slides to the left, the ports D, C are connected. And, by this,
cavitation and pressure rising is prevented.
(Function of the surge cut valve and anti-cavitation valve)
The valve (127) is operated by a little secondary pressure, opens the oil passage between the
port A and the motor suction part, and it prevents the hydraulic motor from cavitation.
Figure 4