U20-3, U25-3 WSM Hydraulic system (Mechanism section)
IV-M-41
[1] Reducer
1) Function
The PHV series travelling motor reducer, which is a simple two-step planetary gear reducer, con-
verts the high-speed revolution of the hydraulic motor to low-speed high torque to obtain case
rotation.
2) Description of operation
In the figure shown to the right, the gear S2
is spline-coupled with the hydraulic motor
output shaft (or they are combined). The
revolution of the gear S2 is single-reduced
through the gears (S2, b2, a2). This single-
reduced revolution is double-reduced
through the gears (S1, b1, a1) spline-
coupled with the carrier 2. The reduced
revolution is transmitted to the rotating
main body through the annular gears a1
and a2, providing travelling driving force.
The reduction ratio of a simple two-step
planetary gear reducer is generally
expressed as shown below.
Where
Zs1, Zs2: Number of teeth of gears s1 and
s2
Za1, Za2: Number of teeth of gears a1 and
a2
Because the PHV series travelling motor is
of the main body rotating type, the
reduction ratio is expressed as shown
below.
R =
Zs1
Zs1 + Za1
Zs2
Zs2 + Za2
×
R’ =
1
1-1/R
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