Negative Brake Function; Planetary Reduction Ratio - Kubota KX080-3 Workshop Manual

WSM KX080-3 Mechanism IV Hydraulic System

4. Negative brake function

Parking brake
The separator discs (1) are in mesh with the housing,
and the friction discs (2) with the cylinder barrel (3).
The separator discs (1) and the friction discs (2) are
pushed against the housing (6) by the springs (4) and
the brake piston (5). The friction between these discs
produces a braking moment, preventing the turning of
the cylinder barrel (3).
When hydraulic oil is required by the motor, the oil
flows from the release port (7) of the parking brake to
the brake piston chamber (8). The oil pressure sur-
passes the spring force and moves the brake piston (5)
to the right. By this, free play is produced between the
separator discs (1) and friction discs (2), and the park-
ing brake is disengaged. When the motor stops, the
sliding valve (9) goes back to the neutral position and
closes the release port (7) of the parking brake.
Thereby, the pressure oil drains from the brake piston
chamber (8) into the motor housing, by which the
spring (4) gets the parking brake (4) reengaged.

5. Planetary reduction ratio

The reduction gears consist of a two-stage planetary
gear, in order to convert the high speed of the motor to
low speed and high torque for the pinion shaft (1). In
the figure at right, the motor-generated driving force is
transmitted in this way: from the drive shaft of the
motor, through the drive gear in the first stage (2), the
planetary gear (3) and the support 1 (4), to the sun
gear in the second stage (5). The sun gear in the sec-
ond stage (5) then transmits the driving force through
the planetary gear (6) and the support 2 (7) onto the
pinion shaft (1), to carry out a swivel motion.
IV-M-80