E-OLSSSection 3.3

E-OLSS: Control Valve.E-OLSS: Control Valve.

Section 3.3Section 3.3

E-OLSSSection 3.3

E-OLSS Control Valve

Control Valve.

The valve is a Open centre Load Sensing System with the jet sensors

installed into the control valve.

Jet Sensors detect the flow of return oil passing through the control valve

and returning to tank. The two pressures Pt and Pd are sent to the

NC valve.

The main relief valve maintains maximum work pressure.

Built into the control valves are the straight travel, arm throttle and swing

priority valves.

Two Stage relief

E-OLSSSection 3.3

E-OLSS Control Valve

Jet Sensors: Levers in Neutral

Oil carry over from the control valve flow through the jet sensors.

When levers are in the neutral position there is a small flow from the pump returning to tank.

The jet stream coming out of the Jet Sensor Orifice is uninterrupted filling Pt sense line back to NC valve.

Jet Sensor Out-put Pressure Pt Jet Sensor Out-put

Pressure Pd

Orifice

Jet Stream

E-OLSSSection 3.3

E-OLSS Control Valve

Jet Sensors: Levers Operated.As the machine starts to operate the oil flow in the control valve increases.

When the differential pressure Pt – Pd reaches 15 Kg/cm2 (at 40 l/min) the relief valve opens.

Now almost all the carry over oil (Qc) is being discharged through the relief valve.A small amount is passing through Jet Sensor Orifice.

Pump pressure Qc

Pt

Pd

Pt (Jet Sensor output pressure)

Pd (Back pressure)

E-OLSSSection 3.3

E-OLSS Control Valve

Straight Travel Valve (PC1250-7).

The straight travel valve is installed into the control valve.

It acts to prevent and deviation in the direction of travel if the boom, arm, or

bucket are operated when the machine is traveling.

E-OLSSSection 3.3

E-OLSS Control Valve

Travel operating Independently

The straight travel solenoid is de-energised, so no pilot pressure is

flowing to the spool.

Ports P1 and P2 are not connected each circuit remains independent.

E-OLSSSection 3.3

E-OLSS Control Valve

When travel and work equipment are operated

together.

The straight travel solenoid is excited and pilot pressure is flowing to spool (6), pushing it across to the

left.

Ports P1 and P2 are now interconnected so the same amount

of oil is delivered to both travel motors evenly.

This prevents travel deviation.

E-OLSSSection 3.3

E-OLSS Control Valve

Control Valve (PC200-5)

Built into the control valve are:

1. Straight Travel valve.

2. Arm Throttle valve.

3. Swing Priority valve.

The control valve is manufactured in two halves, they are bolted together

sharing common galleries.

Straight Travel

Swing Priority

E-OLSSSection 3.3

E-OLSS Control Valve

Arm Throttle Valve.

When the arm control lever and boom control lever are operated at the same time, most of the pressure oil flows t the arm circuit, where the load is less.

When this happens the arm throttle valve is switched and the flow of oil to the arm control valve is restricted.

Arm Operated Independently Arm and Boom

E-OLSSSection 3.3

E-OLSS Control Valve

Swing Priority Valve.

When operating swing and arm at the same time, most of the oil flows to the arm which has less load. The flow to the swing circuit is reduced so arm speed is fast.

To prevent this the swing priority valve is switched to restrict the flow of pressure oil to the arm control valve.

When Swing is not operated with Arm circuit.

When Swing is operated with Arm Circuit.

E-OLSSSection 3.3

E-OLSS Control Valve

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E-OLSSSection 3.3

E-OLSS

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E - OLSSE - OLSS