CB10 Vibratory Asphalt Compactor Machine Systems Control Valve (Drum Offset) Caterpillar

Illustration 1	g06610755
Under Operator Platform (1) Steering control manifold

Steering control manifold (1) is located under the operator platform, above and in front of the pump stack. A panel on the left side of the machine provides access to this component.

Steering control manifold (1) contains components used to control the steering system and the drum offset system.

Illustration 2	g06610768
Steering Control Manifold (2) Compensator spool (3) Counterbalance valves (4) Front clockwise (CW) solenoid (5) Front counterclockwise (CCW) solenoid (6) Margin spool (7) Warmup valve (8) Main relief valve (9) Shunt valve (10) Counterbalance valves (11) Rear clockwise solenoid (12) Rear counterclockwise solenoid

The steering control valve is controlled by the machine ECM. This valve is controlled by four solenoids. The front clockwise and counterclockwise solenoids turn the machine. The rear clockwise and counterclockwise solenoids offset the rear drum to the front drum.

The steering control valve is controlled by the machine ECM. This valve is controlled by four solenoids. Front clockwise solenoid (4) causes the machine to turn right. Front counterclockwise solenoid (5) causes the machine to turn left. Rear clockwise solenoid (11) causes the rear drum to move right. Rear counterclockwise solenoid (12) causes the rear drum to move left. The steering control valve directs oil to one end of the steering cylinder while opening the other end to the hydraulic tank.

When the hydraulic oil temperature is less than 30 °C (86 °F), the machine ECM energizes warmup valve (7). When this happens, the valve directs supply pressure to the network of shuttle valves that monitor the system demand pressures. This action closes the margin spool. When this happens, system pressure increases until it reaches the set point of main relief valve (8) at 20000 ± 1000 kPa (2900 ± 145 psi). The flow of hydraulic oil through the relief valve rapidly heats the hydraulic oil.

Steering shunt valve (9) enables and disables the steering system. The machine ECM energizes the steering shunt solenoid to enable the steering system. In this condition, the shunt valve is closed and oil from the steering pump is routed to the steering control manifold. When the shunt solenoid is de-energized, the shunt valve opens and sends oil from the pump directly to the hydraulic tank. In this condition, the steering system is disabled. The machine ECM disables the steering system when a level-three fault in the circuit to the steering shunt solenoid is detected.

Margin spool (6) regulates the flow of supply oil to the steering system. When the flow of supply oil into the system is greater than the demand of the system, the margin spool directs unused oil into the hydraulic tank.

The shuttle valves (internal, refer to steering hydraulic schematic) compare pressure requirements and send the highest pressure requirement to margin spool (6). One shuttle valve compares the pressure at the rod end of the cylinder and the pressure at the head end of the cylinder. A second shuttle valve compares the highest pressure in the steering cylinder and the external load-sensing pressure signal coming from the side cutter attachment (if equipped).

Counterbalance valves (3) ensure that the steering cylinder will not move unless pressurized oil is in one end. When steering oil is made available to one end of the steering cylinder, this pressure shifts the counterbalance valve on the other end of the steering cylinder. This shift opens the other end of the steering cylinder to the hydraulic tank.

A check valve (internal, refer to steering hydraulic schematic) is installed in parallel with each counterbalance valve (3). This check valve prevents hydraulic oil from flowing out of the steering cylinder unless the corresponding counterbalance valve is open.