2-M5
ZD18(F) · ZD21(F) · ZD28(F), WSM
TRANSAXLE
(4) Check and High Pressure Relief Valve
[Serial No. Affected: above 20001]
The check and high-pressure relief valve consists of
pressure poppet (2), check valve seat (1), relief valve
spring (3), spring guide (4) and check valve spring (5).
The valve is used to prevent an overload that would
happen at a quick start, sudden stop or even during usual
running. This valve doubles as a check valve.
The check and high-pressure relief valves are laid out
facing each other as shown in the figure.
In neutral, both valves are open and charging oil
enters into the main oil circuit through the valves. (A)
At normal operation, the check valve in the high-
pressure side is closed and it pushes and opens the
another one. An excessive charge flow goes through the
charge relief valve into HST housing. (B)
The check and high-pressure relief valve along the
high-pressure line serves as a high-pressure relief valve.
If the pressure exceeds a high-pressure limit level, the
pressure poppet opens itself against the relief valve
spring (3) force and opens the valve seat that is located
between the check valve seat (1) and the pressure
poppet (2). Now the flow goes from P1 to P2 and P3. (C)
If the P1 pressure drops, the relief valve spring forces
the valve seat closed against the pressure. The high-
pressure oil at P1 does not flow to P2 any longer.
As discussed above, the check and high-pressure
relief valve protects engines, pumps, motors, gears and
even the machine itself from overload.
W1015194
3GZAAADKP004A
(1) (2) (3) (4) (5) (6)
P3 P2 P1
P3 P2 P1
P3 P2 P1
(A)
(B)
(C)
Oil temperature Valve operating pressure
50 °C (122 °F)
26.3 to 29.6 MPa
290 to 300 kgf/cm
2
4125 to 4267 psi
(1) Check Valve Seat
(2) Pressure Poppet
(3) Relief Valve Spring
(4) Spring Guide
(5) Check Valve Spring
(6) Valve Plug
(A) In Neutral (Stop)
(B) When Check Valve
Activating (Normal
Operation)
(C) When High Pressure Relief
Valve Activating
To Next Page
Loading...
Need help?
General
