Function Of Swivel Motor; Hydraulic Motor; Relief Valve Functions - Kubota KX080-3 Workshop Manual

WSM KX080-3 Mechanism
b. Function of swivel motor

1. Hydraulic motor

Nine pistons (2) are fitted in the cylinder block (1), and
the valve plate (3) is attached at the end with two half-
moon-shaped ports B and C. The cylinder block (1)
turns itself and is connected by the key with the shaft
(4). On the other hand, the swash-plate (5) is secured
on the housing.
When pressure oil is introduced through the port B, the
swash-late (5) is pushed by each piston (2) with the
force F.
F = P x A
P: Pressure, A: Piston cross-sectional area
The force F, which pushes the pistons (2) onto the
swash-plate (5), is divided in force F1 and 2: Force F1
pushes against the swash-plate and F2 pushes on the
cylinder block (1). The total force of the components in
the turning direction of the pistons at the high-pressure
side produces a rotational force in the cylinder block
(1). This force is transmitted through the key onto the
shaft (4), which is turned. When the pressure oil is
introduced into the port C, on the other hand, the turn-
ing takes place in the opposite direction.
2. Relief valve
Function 1
When the motor gets started:
When the motor gets started, the inertial load becomes
greater, so that the pressure of the oil required for
acceleration rises. If this oil pressure has reached the
preset level of the counterbalance valve, the counter-
balance valve is activated and the oil returns to the port
M2.
In this way, the motor starts running, while the pressure
is balanced by the counterbalance valve. With the rpm
increasing, the balancing rate decreases until finally
the balancing does not take place any longer. In this
manner the shock at the startup is absorbed.
When the motor gets stopped:
When the motor gets stopped, the return circuit is inter-
rupted. Because the motor still turns itself by the inertial
force, however, the pressure at port M2 rises. If this oil
pressure has reached the preset level of the counter-
balance valve, the counterbalance valve is activated
and the oil starts flowing to the port M1. In this way, the
oil flow to the port M1 prevents cavitation that would
occur in shock absorbing during stopping.
IV-M-78
IV Hydraulic System
A
A
1