VALVE, EGR 7095488C2 - Caterpillar

Illustration 4 g00927001
The power train pump is held in the NEUTRAL position by mechanical means when the pump is not driven by the engine. Swashplate (13) is held in the NO FLOW position by two springs (14) and (15) at the pistons. When the engine starts, the pump will run without any displacement. Proportional solenoid valve (4) and (5) must not be energized.Hydraulic Zero Position
Illustration 5 g00927006
After the engine has been started, the power train pump is held in the NEUTRAL position by hydraulic pressure from the charge pump. This pressure is routed to the servo control valve. The two proportional solenoid valves (4) and (5) are not energized at this time. The charge pressure that reaches servo control valve (6) through charge pressure line (19) acts as a control pressure.
Illustration 6 g00927007
In the NEUTRAL position, pilot valve (10) will connect control piston (17) and control piston (18) with the control pressure. This will retain the swashplate in the NEUTRAL position.Charge Pump
Illustration 7 g00927054
Charge pump oil is used in the drive loop to prevent power train pump (21) from cavitating. The charge pump oil is also used to control the displacement of power train pump (21) and the power train motor. Charge pump (11) is mounted on power train pump (21). Charge pump (11) is driven by a through shaft in power train pump (21). Charge pump (11) is a gear pump that provides pressure in the charge circuit. The oil pressure in the charge circuit is controlled by charge pressure relief valve (8) and by cold start valve (20) .Charge pump oil flows through cold start valve (20). Cold start valve (20) responds only if the back pressure in the cooling system and the back pressure in the filtration system exceeds the set pressure of 3000 kPa (435 psi).The charge pump oil then flows to power train oil filter (22). Power train oil filter (22) provides filtration in the charge circuit. This filter is protected by a bypass valve.If the filter element fills with debris, the restriction to the hydraulic oil flow causes the hydraulic oil pressure to increase. If the hydraulic oil pressure increases to 172 2 kPa (24.9 .3 psi), the bypass valve will open. This allows the hydraulic oil to bypass the filter element. When the hydraulic oil bypasses the filter element, the debris in the hydraulic oil may damage other system components. Make sure that correct maintenance is performed, so that the filter element does not block the flow of clean hydraulic oil to the charge system.Charge pump oil then flows back into the power train pump and flows to the servo control of the power train motor.Servo Control Operation
Illustration 8 g00927092
Pilot valve (10) is used to actuate the servo control valve (6). Pilot valve (10) is integrated into servo control valve (6). Pilot valve (10) is moved by actuator piston (9). Actuator piston (9) is held in the CENTER position by two springs (25). Pilot valve (10) and actuator piston (9) are mechanically connected to