BENDIX M-40QR Dati di servizio - Pagina 5

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ANTILOCK APPLY MODE

If a service brake application is made and the antilock

system detects an impending wheel lockup, the antilock

controller will make a controlled brake application using

the modulator.

In order to control the brake application, the coils of the two

solenoid valves contained in the modulator are energized,

or de-energized, in a pre-programmed sequence by the

antilock controller. When a solenoid coil is energized,

and – depending on whether the exhaust or hold solenoid

is energized – it either opens or closes, thereby causing

the exhaust or reapplication of air pressure to the brake

actuator. The solenoids in the modulator are controlled

independently by the Electronic Control Unit (ECU).

ANTILOCK EXHAUST MODE

When wheel lock is detected or imminent, the antilock

controller energizes the supply and exhaust solenoids in

the modulator.

Further delivery of air to the brake chamber is prevented,

and air is allowed to exhaust through the exhaust port.

ANTILOCK HOLD MODE

The antilock controller will place the modulator in the hold

position when information from the wheel speed sensors

shows that the correct wheel speed (braking force) has

been attained. The antilock controller will also place

the modulator in the hold position – prior to entering the

reapply mode – when it detects recovery from a locked

wheel condition.

In this mode of operation, the exhaust passage is sealed,

holding the air pressure in the brake chamber at that level.

At the same time, no application air is permitted to flow to

the brake chamber.

The modulator can enter both the antilock exhaust or

reapply mode from the antilock hold mode depending on

the needs of the antilock controller.

ANTILOCK "REAPPLY" MODE

If the antilock controller senses that wheel speed has

increased sufficiently enough to allow re-application of

braking pressure, without further wheel lock-up, it permits

the supply air to re-apply air to the brakes in the same

manner it did during a non-antilock event.

PREVENTIVE MAINTENANCE

GENERAL

Read and follow the General Safety Guidelines on

page 2 of this document.

Perform the tests and inspections presented at the

prescribed intervals. If the modulator fails to function as

described, or if the leakage is excessive, replace it with a

new Bendix

brand unit, available at any authorized parts

outlet.

EVERY MONTH, 10,000 MILES, OR

350 OPERATING HOURS

1. Remove any accumulated contaminates and visually

inspect the exterior for excessive corrosion and physical

damage.

2. Inspect all air hoses and wire harnesses connected to

the modulator for signs of wear or physical damage.

Replace as necessary.

3. Test air line fittings for leakage and tighten or replace

as necessary.

4. Perform the routine OPERATION & LEAKAGE TESTS

described below.

OPERATION & LEAKAGE TESTS

OPERATION TEST

This test uses the Chuff Test (described on page 3).

To properly test the function of the modulator will require

two (2) service technicians.

1. Park the vehicle on a level surface and block or chock

the wheels. Release the parking brakes and build the

air system to governor cut-out.

2. Turn the engine ignition key to the OFF position then

make and hold a full brake application.

3. With the brake application held and one (1) service

technician posted at one (1) of the modulators, turn

the vehicle ignition key to the ON position. One or

two short bursts of air pressure should be noted at the

modulator exhaust. Repeat the test for each modulator

on the vehicle. If at least a single burst of exhaust is

not noted or the exhaust of air is prolonged and not

short, sharp, and well defined, perform the Electrical

Tests.