SHOE-TRACK 3261134 - Caterpillar

Gradual Right Turn
Control Valve Operation for a Gradual Right Turn
Note: The steering clutch and the brake are not engaged.
Illustration 3 g02799317
Steering and brake control valve (Gradual Right Turn)
(1) Circuit for clutch oil
(2) Clutch spool for right steering
(3) Parking brake valve
(4) Secondary brake valve
(G) Solenoids The steering and brake control valve has solenoids (G) which control the position of the pressure reducing spools in the steering and brake control valve.As the operator begins to pull the right steering control lever, the pulse width modulated sensors send a signal to the electronic control module. This signal is sent in order to decrease the current going to solenoids (G) for the right clutch.The decreased current causes a decrease in pilot oil pressure which causes reducing spool (2) to shift to the left. This shift exhausts the oil in the clutch circuit. When the oil is exhausted the clutch oil pressure is lowered.The current that goes to the solenoid for the valve is dependent upon the position of the control lever. The solenoid sets the pilot oil pressure. The pressure in the clutch circuit is directly affected by the position of the control lever.When the control lever is pulled back the clutch pressure is reduced. When you pull back the control lever further, the clutch pressure is reduced until the pressure reaches 0 kPa (0 psi) and the clutch is released. The machine will then make a gradual right turn.Sharp Right Turn
Control Valve Operation for a Sharp Right Turn
Note: The steering clutch is not engaged. The brake is engaged.
Illustration 4 g02799357
Steering and brake control valve (Sharp Right Turn)
(3) Parking brake valve
(4) Secondary brake valve
(5) Brake spool for right steering
(F) Valve
(G) Solenoids The steering and brake control valve has solenoids (G) which control the position of the pressure reducing spools in the steering and brake control valve. These spools adjust the clutch and brake pressure when the control levers are moved.In order to make a sharp right turn, the operator pulls the steering control lever backward all the way. During the first movement of the control lever, the clutch pressure is modulated to 0 kPa (0 psi). This is the same pressure as a gradual right turn.As the operator continues to pull the control lever backward, the pulse width modulated sensors send a signal to the ECM. This signal decreases the current to the right solenoid (G) for the brake. This decreases pilot oil pressure which causes reducing spool (5) to shift to the left. This shift to the left exhausts the oil in the right brake circuit which drops the brake pressure.The current that goes to the solenoid is determined by the position of the control lever. Valve (F) sets the pilot pressure. The pressure in the brake circuit is directly affected by the position of the control lever.When you pull back the control lever further, the brake pressure is reduced until the brake is fully engaged. This operation results in a sharp right turn of the machine. Residual oil pressure is maintained on