Check Valve And High Pressure Relief Valve - Kubota ZD221-48 Workshop Manual

Z0221, WSM
TRANSAXLE
(3) Check Valve and High Pressure Relief Valve
(A)
(1) (2) (3) (4) (5) (6)
(8)
(C)
3GZAAADKP004A
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. (8)
The check and high-pressure relief valve along the
high-pressure line serves as a 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.
Oil temperature
Valve operating pressure
23.5 to 25.5 MPa
50°C (122 OF) 240 to 260 kgflcm
2
3408 to 3698 psi
(1) Check Valve Seat
(A) In Neutral (Stop)
(2) Pressure Poppet (8) When Check Valve
(3) Relief Valve Spring Activating (Normal
(4) Spring Guide Operation)
(5) Check Valve Spring (C) When High Pressure Relief
(6) Valve Plug Valve Activating
P1 : Forward
P2: Change
P3: Reverse
W1013434
2-M4