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| Illustration 1 | g02178194 |
(1) Solenoid valve (2) Steering cylinders (3) Steering control valve (4) Spool (5a) Solenoid for right turn (5b) Solenoid for left turn (6) Steering pilot control valve (7) Pressure reducing valve (8) Control manifold (9) Pilot filter (10) Check valve (11) Relief valve (12) Electric drive pump (13) Electric drive motor (14) Hydraulic filter (15) Implement and steering pump (16) Hydraulic tank (17) Check valve (18) Pressure sensor (19) Shuttle valve (20) Priority valve (21) Flow compensator valve | |
Secondary Steering Pump
When the secondary steering pump is activated, the machine must be in motion. The secondary steering can be activated in test mode or automatic mode.
Hydraulic oil is supplied from hydraulic tank (16) to secondary steering pump (12). Secondary steering pump (12) pumps hydraulic oil to control manifold (8). Hydraulic oil flows through control manifold (8) to steering control valve (3). When the operator signals for a turn, steering control valve (3) supplies a regulated amount of hydraulic oil to steering cylinders (2) .
Two check valves are installed in the steering system in order to prevent a loss of hydraulic oil backward through the system.
Check valve (17) is installed in the line between the implement and steering pump (12) and control manifold (8). Check valve (17) prevents hydraulic oil from flowing backward to the implement and steering pump (15) .
Check valve (10) is installed in the line between secondary steering pump (12) and control manifold (8). When secondary steering pump (12) is not running, check valve (10) will prevent loss of oil backward through the system. Check valve (10) prevents the loss of oil from control manifold (8) backward through the secondary steering pump.
When the system pressure exceeds the relief valve setting, relief valve (11) will open. Relief valve (11) directs oil back to hydraulic tank (16) .
Secondary Steering Pilot Valve
When solenoids (1) are not working properly, secondary steering solenoids (5a) and (5b) will be turned on by the transmission/chassis ECM.
Priority valve (20) will be held to the left by the force of the spring. Pump flow will be directed to flow compensator valve (21). Pump flow will satisfy the requirements of the steering system. Pump flow will travel through pressure reducing valve (7) to secondary steering pilot valve (6). Pressure reducing valve (7) will be held open by the spring until the pilot system pressure is 3000 kPa (435 psi). The transmission/chassis ECM will energize solenoid (5a) when the joystick is moved to the left turn position by the operator. Solenoid (5a) will direct pilot oil to the left side of spool (4). Spool (4) will shift to the right. Pump oil will be directed past spool (4) to steering cylinders (2) .