Honda Acura NSX 1991 Service Manual page 721

ALB Description
Features/Construction/Operation
Pressure Switch
The pressure switch monitors the pressure accumulation (pressure from the pump) in the accumulator and is turned off
when the pressure becomes lower than a prescribed level. When the pressure switch is turned off, the switching signal is
sent to the control unit. Upon receiving the signal, the control unit activates the pump motor relay to operate the motor. If
the pressure doesn't reach the prescribed value, the system indicator light is turned on.
Operation
When the pressure in the accumulator rises, the Bourdon tube in the pressure switch deforms outwards. When the free
end of the Bourdon tube moves more than the prescribed amount, the micro-switch is activated by the force of the spring
attached to the sensing lever. When the pressure in the accumulator decreases due to anti-lock brake system operations,
the Bourdon tube moves in the direction opposite to the one described above, and the micro-switch is eventually turned
off. Upon receiving this signal, the control unit activates the motor relay to operate the motor.
Power Unit
The power unit is composed of a motor and a plunger-type pump. This unit transmits the revolution of the motor to the
plunger by way of an eccentric bearing and supplies high-pressure brake fluid to the accumulator by the effect of the
reciprocating movement of
When the pressure in the accumulator drops below the prescribed pressure level, the pressure switch gives an OFF-
signal. The control unit turns the motor relay ON to start the operation of the pump, upon the reception of this signal and
a signal from the wheel sensor that the vehicle is running at a speed greater than 10 km/h. When the pressure in the ac-
cumulator attains the prescribed pressure, the control unit turns the motor relay OFF approximately three seconds after
the unit receives an ON-signal from the pressure switch. By this, the high-pressure in the accmulator
The control unit turns the pump off and lights the system indicator light if the accumulator pressure does not reach the
prescribed level after the pump has run continuously for 120 seconds.
(cont'd)
the plunger.
SENSING LEVER
'PUMP
is maintained.