jcb JS70 Service Manual

Multiple Valve
Operation
Relief Valve (E)
This is a direct driven type relief valve to produce the inlet
pressure in the valve.
When the pressure at Port P1 rises, the poppet 4 moves
towards the left and connects P1 and T, and reduces the
inlet pressure.
Check Valve
This is a poppet type check valve to protect the reverse flow
of pressurised oil from ACC to P1.
Shut Off Valve
Solenoid Valve 1 (SOL1)
The solenoid valve 1 cuts the pilot pressure supply and
operates the shut off valve.
The normal closing circuit in neutral condition has voltage
applied from the shut off side to port T. The solenoid 20 is
operated and the spool 24 is activated by the push rod.
Pressurised oil is supplied to shut off the valve at port T.
Shut Off Valve 1
The hydraulic pilot switch valve is operated from the pilot
pressure from the solenoid valve 1.
The pressurised oil from P1 is cut in the neutral condition (P’
to T).
When the valve is pressurised with pilot pressure, the load to
spring 9 is overcome, which allows the spool 18 to move
until the plug 31 connects Port P1 to P’ and cuts the flow at
port T.
Shut Off Valve 2 (SOL2)
This hydraulic pilot switch valve operates P’ pressure as the
pilot pressure (ON-OFF of the shut off valve).
Ports P1,B1 and B2 are connected in the neutral condition.
When the pilot pressure is engaged, the load on the spring 7
is overcome moving the spool 16 until it touches the plug 29
and cuts off the connection between P1, B1 and B2.
Pressure Reducing Valve
Solenoid Valve 2 (SOL2)
This valve is connected to the spring chamber (T circuit) of
the pressure reducing valve and supplies pilot pressure to
the spring chamber, It also operates the pressure reducing
valve connections to the T of the spring chamber and
controls the lock.
There is a normal open circuit during neutral condition with
voltage applied (P to pressure reducing valve). The solenoid
20 is operated, the spool 23 of the pressure reducing valve
is operated by the push rod and cuts P and connects flow to
the pressure reducing valve to T.
Pressure Reducing Valve
During Operation
(Solenoid valve 2 - ON, Spring Chamber - T).
Reduces the inlet pressure to the set pressure of the
pressure reducing valve and supplies the shuttle valve.
The pressurised oil from port P passes through the small
hole inside the spool 13 and through the spool head to the
shuttle valve.
The spool 13 is moved to the position for balancing the
spring load with the pressure of the spool head.
If the pressure increases on the spool head, the spool 13
moves and the P circuit is closed on the (a) section and the
T circuit is opened. The oil pressure of the spool passes
through the small hole in spool 13 and pressure is reduced.
(Pressure on the spring head 21 reaches the set pressure of
the pressure reducing valve).
When the spool head pressure drops down below the spring
load F (set pressure of the pressure reducing valve), the
spool 13 is moved back to the position where T is closed
and P is opened.
The spool head pressure rises to balance the spring load F
(set pressure of the pressure reducing valve). With the
opening and closing of P and T pressure is maintained.
During Locking
(Solenoid valve 2 - OFF, pressure to spring chamber).
Suppies the inlet pressure directly to the shuttle valve.
The pressurised oil from port P1 passes through the small
hole inside the spool 13 and through the spool head to the
shuttle valve. Pressurised oil with identical pressure is
supplied from the solenoid valve 2 to the spring chamber.
The pressure balance is spool head pressure<spring
chamber pressure plus spring pressure 21. To lock the
spool 13, the inlet pressure is directly supplied to the shuttle
valve without pressure reducing operation.
Shuttle Valve
This valve is to connect the higher pressure of the
pressurised oil from the pressure reducing valve and port A2
to the solenoid valve 4
Solenoid Valve 3
This valve is identical to solenoid valve 1 and is designed to
cut and supply pressure from circuit P’ to port A1.
Solenoid Valve 4
This valve is identical to solenoid valve 2 and is designed to
cut and supply pressure from the shuttle valve to port A3.
60 - 1
Section E Hydraulics
9803/6020
Section E
60 - 1
Issue 1
Multiple Valve

jcb JS70 Specifications

General

Brand	jcb
Model	JS70
Category	Excavators
Language	English