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| Illustration 1 | g01083279 |
Gear pump | |
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| Illustration 2 | g01083282 |
(1) Lines to brake accumulators (2) Shuttle valve (3) Pressure sensor for brake charging (4) Check valve (5) Orifice (6) Braking and hydraulic fan pump (7) Line from tank (8) Solenoid valve for brake charging (9) Line to fan motor (10) Flow control valve for the brake | |
The hydraulic oil flows into pump (6) from the line from tank (7). The oil flows from the pump through check valve (4) to shuttle valve (2). The shuttle valve directs the flow of oil to the accumulator with the lowest pressure through the lines to the brake accumulators (1). The pressure sensor for the brake system (3) sends a signal to the machine ECM that is proportional to the pressure in the brake accumulators. When the accumulator pressure rises, the machine ECM sends a signal to the solenoid valve for brake charging (8) in order to shift the solenoid valve for brake charging more open.
When the solenoid valve for brake charging (8) shifts open, the pressure drop across orifice (5) increases. When the pressure drop across orifice (5) increases, flow control valve (10) for the brakes will shift open. When flow control valve (10) for the brakes shifts open, oil from pump (6) is also directed to the line to the fan motor (9). Check valve (4) will close in order to prevent the flow of oil in the brake accumulators to the pump.
Note: The solenoid valve for brake charging (8) is a proportional valve. The amount of flow that flows through flow control valve (10) for the brakes is proportional to the amount of flow that flows through solenoid valve for brake charging (8). The amount of flow that flows through solenoid valve for brake charging (8) is proportional to the amount of electric current that is sent from the ECM to solenoid valve for brake charging (8) .
After several applications of the brakes, the pressure in the brake accumulators will decrease. Then, the machine ECM will send a signal to the solenoid valve for brake charging (8) in order to close the solenoid valve for brake charging (8). When the solenoid valve for brake charging closes, the pressure drop across orifice (5) will decrease. When the pressure drop across orifice (5) decreases, flow control valve (10) for the brakes will close in order to direct more oil to the accumulators. This will charge the brake accumulators in order to provide the proper brake system pressure.