2-53
TWO SPEED CHANGE MECHANISM
When running at 1st speed (low speed)
Port B(High pressure)
Port C(Low pressure)
Valve plate(25)
Spring(42)
Spool(41)
Low pressure
Spring(20)
Swash plate control piston(19)
Face a
Swash plate(5)
Spring(9)
Piston
sub assy(15)
Face c
Face b
L1
L
0
Fp + Fs2
Pi1
Pi2
M1
M2
Steel ball(6)
F + Fs1
At 1st speed(low speed)
3)
R35Z72TM08
(1)
Swash plate (5) has three faces, from "a" to "c", as shown below in the figure and installed in the
flange holder that is piston motor housing with two steel balls (6) in the condition where it can be
tilted.
When the control valve is set to the 1st speed position, spool (41) is placed in the position shown
below in the figure by the force of spring (42), and the passage of swash plate control piston (19)
passes across the Pi1 and Pi2 port positions and led to the tank port. Therefore, the force pushing
up the swash plate control piston (19).
Fp : Swash plate control piston thrust
Ap : Swash plate control piston pressure receiving area
P : Pressure
Fp = (Ap
Ý
P) = 0
When steel ball (6) is placed on the tilting center, the balance of moment acting on swash plate (5)
is in the condition of (
Į
F+Fs1)
Ý
L1 > (Fp+Fs2)
Ý
Lo depending on the total
Į
F of driving force of
piston sub assy (15) and the force of spring (9) Fs1 and Fs2, then swash plate (5) stables at the
face a and the swash plate angel is
ɷ
, and consequently the motor speed corresponding to the 1st
speed, low speed, is obtained.
(
(
Į
F+Fs1)
Ý
Ý
L1 > (Fp+Fs2)
Ý
Lo
