Inlet Solenoid Valve

Inlet solenoid valves control the brake pressure of each wheel by combining the operation of the outlet solenoid valve. The ECU changes the electric current in the solenoids of the inlet solenoid valve (2 way, 2 position electromagnetic valve) to move the tappet and change the fluid pressure to “Increase Mode”, “Hold Mode”, or “Decrease Mode”.

1. Increase Mode

2. Hold and Decrease Mode

3. Tappet

4. Valve Body

5. From Master Cylinder

Outlet Solenoid Valve

Outlet solenoid valves control the brake pressure of each wheel by combining the operation of the inlet solenoid valve. The ECU changes the electric current in the solenoids of the outlet solenoid valve (2 way, 2 position electromagnetic valve) to move the armature and change the fluid pressure to “Increase Mode”, “Hold Mode”, or “Decrease Mode”.

1. Decrease Mode

2. Increase and Hold Mode

3. Armature

4. Valve

5. To Reservoir

Reservoir

When the passage opens between the caliper and the reservoir with the outlet solenoid valve in “Decrease Mode”, the brake fluid flows into the reservoir by pushing the piston, stays there temporar- ily, and then returns to the master cylinder. With the outlet solenoid valve “Increase or Hold Mode”, the pump returns the remaining brake fluid in the reservoir to the master cylinder.

1. From Outlet Solenoid Valve

2. To Pump

Pump Motor

The pump motor operates the pump, supply or return the brake fluid from the pump.

Pump

The pump operates continuously when the ABS is activated. The pump is driven by the motor and supply the brake fluid to the caliper or return the brake fluid in the reservoir to the master cylinder. The piston is reciprocated by the eccentric cam [A] on the end of the motor shaft and the pump sucks in or discharge the brake fluid.

When the pump pulls fluid in, the piston [B] is moved right by the force of the spring [C]. At this time, the spring [D] is compressed by the pressure of the brake fluid in the reservoir to open the inlet valve [E] and the brake fluid flows into the cylinder [F]. The outlet valve [G] is held closed by the force of the spring [H].

When the pump discharges the brake fluid, the inlet valve [E] is closed by the spring [D], and the piston [B] is moved left by the cam [A], producing pressure in the cylinder [F]. The pressure pushes the spring [H], opens the outlet valve [G], and the brake fluid returns to the master cylinder.

Spring [C]

ABS Solenoid Valve Relay

ABS solenoid valve relay supply or intercept the power to the inlet or outlet solenoid valves.

ABS Motor Relay

ABS motor relay supply or intercept the power to the pump motor.

ECU

ECU inputs the sensor signal.

ECU calculates the wheel condition for the slip. ECU controls the hydraulic unit.

ECU sends the actuating signals to the ABS indicator light (LED).

ABS Operation

The ABS has two independent hydraulic lines, one for the front wheel and the other for the rear wheel. The front wheel system is explained here and is identical to the rear wheel system.

ABS in Action

(Increase Mode)

When the caliper fluid pressure is to be increased, first the tappet of inlet solenoid valve opens (normally open). The brake fluid flows through the valve body as shown in the diagram below to increase the brake fluid pressure in the caliper. The master cylinder pressurizes to the brake caliper directly, increasing the braking force.

1. Brake Lever

2. Front Inlet Solenoid Valve

3. Pump Motor

4. Pump

5. Front Reservoir

6. Front Outlet Solenoid Valve

7. Front Caliper

(Hold Mode)

When the caliper fluid pressure is to be hold, the tappet of inlet solenoid valve closes, and the passage (master cylinder side) to the valve body is intercepted. No matter how hard the brake lever is pulled, the brake fluid pressure in the caliper is maintained at a given level.

1. Brake Lever

2. Front Inlet Solenoid Valve

3. Pump Motor

4. Pump

5. Front Reservoir

6. Front Outlet Solenoid Valve

7. Front Caliper

(Decrease Mode)

When the caliper fluid pressure is to be decreased, the tappet of inlet solenoid valve closes, and the passage to the valve body is intercepted. The valve of outlet solenoid valve is opened by the operation of the armature, and the brake fluid flows to the reservoir. ECU operates pump, and the pump returns the brake fluid in the reservoir to the master cylinder. The brake fluid pressure is decreased, and the wheel is prevented from locking.

1. Brake Lever

2. Front Inlet Solenoid Valve

3. Pump Motor

4. Pump

5. Front Reservoir

6. Front Outlet Solenoid Valve

7. Front Caliper

ABS Disabled (Conventional Mode)

During cruising (without braking) or in case of a malfunction with the ABS, the ECU stops operating. This is “Conventional Mode”.

When the caliper fluid pressure is to be increased, first the tappet of inlet solenoid valve opens (normally open). The brake fluid flows through the valve body as shown in the diagram below to increase the brake fluid pressure in the caliper. The master cylinder pressurizes to the brake caliper directly, increasing the braking force.

1. Brake Lever

2. Front Inlet Solenoid Valve

3. Pump Motor

4. Pump

5. Front Reservoir

6. Front Outlet Solenoid Valve

7. Front Caliper

Riding Characteristics of ABS

ABS is designed to help prevent the wheels from locking up when hard brakes are applied while running straight. The ABS automatically regulates brake force. Intermittently gaining gripping force and braking force helps prevent wheel lock-up and allows stable steering control while stopping.

Brake control function is identical to that of a conventional motorcycle. The brake lever is used for the front brake and the brake pedal for the rear brake.

Although the ABS provides stability while stopping by preventing wheel lock-up, remember the fol- lowing characteristics:

○^{ABS cannot compensate for adverse road conditions, misjudgement or improper application of}

brakes. You must take the same care as with motorcycles not equipped with ABS.

○^{ABS is not designed to shorten the braking distance. On loose, uneven or downhill surfaces, the}

stopping distance of a motorcycle with ABS may be longer than that of an equivalent motorcycle

without ABS. Use special caution in such areas.

○^{ABS will help prevent wheel lock-up during straight-up braking, but it cannot control wheel slip which}

may be caused by braking during cornering. When turning a corner, it is better to limit braking to

the light application of both brakes or not to brake at all. Reduce your speed before you get into the corner.

○^{The ECU integrated in the ABS compare vehicle speed with wheel speed. Since non-recommended}

tires can affect wheel speed, they may confuse the ECU, which can extend braking distance.

NOTE

○^{When the ABS is functioning, you may feel a pulsing in the brake lever or pedal. This is normal.}

You need not suspend applying brakes.

○^{Immediately after turning the ignition switch on, you may hear a click of the relay operating. This}

is the sound of self-checking and is quite normal.

○^{ABS does not function at the speed of approx. 6 km/h or below.}

○^{ABS does not function if the battery is discharged.}