ABS HU PART CONSTRUCTION/OPERATION
id041300185400
Construction
• The ABS HU mainly consists of the inlet/outlet solenoid valves, pump motor (pump) and reservoir.
Function Of Main Component Parts
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Part name
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Function
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Inlet solenoid valve
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• Adjusts the fluid pressure in each brake system according to ABS CM signals.
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Outlet solenoid valve
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• Adjusts the fluid pressure in each brake system according to ABS CM signals.
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Reservoir
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• Temporarily stores the brake fluid from the caliper piston to ensure smooth pressure reduction.
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Pump
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• Returns brake fluid stored in the reservoir back to the master cylinder.
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Pump motor
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• Operates the pump according to ABS CM signals.
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Hydraulic Circuit Diagram
Operation
During normal braking
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• During normal braking, the solenoid valves are not energized and all of them are off. When the brake pedal is depressed, brake fluid pressure is transmitted from the master cylinder, through the inlet solenoid valves, and then to the caliper piston. (The figure shows control for one front wheel only.)
Solenoid valve operation table
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Inlet solenoid valve
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Outlet solenoid valve
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Pump motor,
pump
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LF
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RF
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LR
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RR
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LF
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RF
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LR
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RR
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OFF (open)
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OFF (closed)
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Stopped
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Hydraulic Circuit Diagram
During ABS and EBD control
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• When wheel lock-up is about to occur, the inlet and outlet solenoid valves are energized and controlled in three pressure modes (increase, maintain, or reduction), thereby adjusting brake fluid pressure. Brake fluid during pressure reduction is temporarily stored in the reservoir and afterwards the pump motor operates the pump to return the fluid to the master cylinder. (The figure shows control for one front wheel only.)
Solenoid valve operation table
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Inlet solenoid valve
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Outlet solenoid valve
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Pump motor,
pump
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LF
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RF
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LR
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RR
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LF
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RF
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LR
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RR
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During pressure increase mode
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OFF (open)
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OFF (closed)
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Stopped
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During pressure maintain mode
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ON (closed)
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OFF (closed)
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Stopped
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During pressure reduction mode
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ON (closed)
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ON (open)
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Operation
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Hydraulic Circuit Diagram
