jcb Mini CX - Page 205

Section E - Hydraulics
Operation Description
Transmission Operation - 4WD Series 2 Machines
E-35 E-35
9803-9340-8
Reverse
K Fig 28. ( T E-36)
When the operator selects forward drive, solenoid 3b is
energised causing direction control valve 3 to direct pilot
pressure from the DA valve 6 to the swash control piston
2. As the pilot pressure increases, due to engine speed
increase when the accelerator is depressed, the swash
plate control piston 2 moves to one side causing the swash
plate to swivel. This causes the oil to be pumped from the
A port of the pump drive circuit to the B port which
increases the pressure on the B side, thus driving the
motors and causing the machine to move backwards.
Oil pressure is fed to all the motors M1, M2, M3 and M4
simultaneously which causes them to rotate. Due to how
the “Twin-Lock” system works, whilst in reverse, the
exhausted oil from the front motors M3 and M4 is fed to the
rear motors M1 and M2 where it is recombined with the oil
that went directly to the rear motors and all the oil is sent
back to the pump. No oil is purged out of the drive circuit
when the machine is in reverse.
Pump feed pressure to the motor is controlled by the
pressure cut-off valve 4 whilst the non return valve in 5b
stays closed preventing constant high pressure being fed
back to the charge pump 8. Should an overload situation
occur in the high pressure side of the loop circuit, the high
pressure relief valve in 5b will open briefly releasing oil
which will then flow into the pump case via charge
pressure relief valve 7. The charge pump 8 replaces any
oil losses from purge, leakage and relieved oil to the drive
loop via the non return valve in 5a which is the low
pressure side of the loop circuit. Any surplus charge oil is
released into the pump case through the charge pressure
relief valve 7 where it returns to tank via oil cooler C.
Key
C Cooler
P1 Transmission Pump
M1 Motor
M2 Motor
M3 Motor
M4 Motor Shuttle Valve
S Suction strainer
T Tank
2 Swash Control Piston
3 Direction Control Valve
4 Pressure Cut-off Valve
5a High Pressure Relief Valve
5b High Pressure Relief Valve
6 Displacement Angle Control Valve
6a Inching Pedal Connection
7 Charge Pressure Relief Valve
8 Charge Pump
10 Variable Displacement Pump
11a Series Line & Hose Protection Valve
11b Series Line & Hose Protection Valve
12 Brake Valve
13 Hydraclamp Valve
14 Porting Block
14a Purge Valve
Key