Yamaha XT1200Z 2010 Service Manual page 26

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Hydraulic unit assembly
The hydraulic unit assembly "1" is composed of hydraulic control valves (outlet solenoid valves, inlet
solenoid valves, a shuttle solenoid valve, and a separation solenoid valve), buffer chambers, damping
chambers, hydraulic pumps, an ABS motor, hydraulic pressure sensors (front brake master cylinder
pressure sensor, rear brake master cylinder pressure sensor, and rear brake caliper pressure sensor),
and an ABS ECU. The hydraulic unit adjusts the front and rear wheel hydraulic pressure to control the
wheel speed according to signals transmitted from the ABS ECU.
Hydraulic control valves
There are four types of hydraulic control valves: inlet solenoid valve, outlet solenoid valve, shuttle so-
lenoid valve, and separation solenoid valve. The electromagnetic force generated in the inlet solenoid
valve varies proportionally with the duty cycle control voltage that is supplied to it. Since this voltage is
continuously variable, the solenoid valve moves smoothly and the hydraulic pressure is adjusted linear-
ly.
1. Inlet solenoid valve
This valve is open during normal braking and UBS operation.
The valve opens and closes during ABS operation to adjust the hydraulic pressure input from the
brake lever or brake pedal.
2. Outlet solenoid valve
This valve is closed during normal braking and UBS operation.
The valve opens during ABS operation to reduce the hydraulic pressure.
3. Separation solenoid valve
This valve is open when the brake pedal is depressed, but the valve opens and closes during UBS
operation to adjust the hydraulic pressure.
The valve opens if the ABS operates when the brake pedal is depressed, but the valve opens and
closes to adjust the hydraulic pressure if the ABS operates during UBS operation.
4. Shuttle solenoid valve
This valve is closed when the brake pedal is depressed, but the valve opens during UBS operation
to pressurize the rear brake caliper.
The valve closes if the ABS operates when the brake pedal is depressed, but the valve opens and
closes to adjust the hydraulic pressure if the ABS operates during UBS operation.
ABS ECU
The ABS ECU is integrated with the hydraulic unit to achieve a compact and lightweight design. As
shown in the following block diagram, the ABS ECU receives wheel sensor signals from the front and
rear wheels and also receives signals from other monitor circuits.
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