2-49
2. FUNCTION
HYDRAULIC MOTOR
Shaft(2)
Swash plate(5)
Piston sub assy(14)
Cylinder block(7)
Valve plate(21)
Port C
Port B
1)
R35Z72TM03
Nine piston assemblies (14) are assembled in cylinder block (7). The end face of cylinder block (7)
is in contact with valve plate (21) having two crescent shaped ports, B and C (high and low pressure
ports).
When supplying pressure fluid (pressure P) to B port, swash plate (5) is pushed by the force of
piston sub assemblies having F = P
¡⁄
A (A : piston pressure area). Piston assemblies receive the
reaction force against it, and produce the reaction force (Ft) in rotating direction. The total force of
high pressure side piston assemblies in rotating direction produces a rotating force in the cylinder
block, and the torque is transmitted to shaft (2) through the spline resulting in the rotation of the
shaft.
According to the above working principle, the output torque and rotating speed of the piston motor
are determined by supply pressure (P) and flow rate (Q), and are calculated by the following
equation.
P
Ý
D
Ýɽ
m
T =
2*
ӕ
Q
Ý
10
3
Ýɽ
v
N =
D
T : Output torque [N
Â
m]
N : Speed of rotation [rpm]
P : Working pressure [MPa]
Q : Flow rate [L/min]
D : Theoretical displacement [cm
3
/rev]
ɽ
m : Mechanical efficiency
ɽ
v : Volumetric efficiency
