BENDIX MC-12 MODULATOR CONTROLLER ASSY Guide de dépannage télécharger pdf (Page 37)

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Section 6: Antilock Braking Systems

For color schematics of tractors and trucks see the fold-out covers of this handbook.

ABS Components

Typical ABS components (for trucks and tractors) are:

• Wheel speed sensors (such as the Bendix

WS-24

™

wheel speed sensors shown on this

page). Each sensor is installed with a Bendix

Sensor Clamping Sleeve. Vehicles have an

exciter ring (or “tone ring”) as part of the wheel

assembly, and as the wheel turns, the teeth of

the exciter ring pass the wheel speed sensor,

generating an alternating current (AC) signal,

which varies in voltage and frequency as the

wheel speed changes. The ECU receives the

AC signal and can then monitor how fast the

wheel is turning.

• Pressure Modulator Valves (PMV) (such as the

Bendix

M-32

™

or M-32QR

™

pressure modulator

valves - shown on this page). PMVs use

solenoids with the ability to apply, hold, or release

the air pressure being delivered to the brakes to

optimize brake performance. Four, ﬁ ve, or six of

these valves may be used depending on ECU

model and vehicle conﬁ guration.

Bendix

Antilock Braking Systems (ABS) use wheel

speed sensors, ABS pressure modulator valves, and

an Electronic Control Unit (ECU) to control either

four or six wheels of a vehicle. Bendix ECUs are

able to optimize slip between the tire and the road

surface by monitoring individual wheel turning motion

during braking, and adjust or pulse the brake pressure

at the wheel end. When excessive wheel slip, or

wheel lock-up, is detected, the ECU will activate the

Pressure Modulator Valves similar to a driver pumping

the brakes. The ECU, however, is able to pump the

brakes on individual wheels (or pairs of wheels),

independently, and with greater speed and accuracy

than a driver.

In addition to the ABS function, premium models of

the ECUs provide an Automatic Traction Control

(ATC) feature. Bendix ATC can improve vehicle

traction during acceleration, and lateral stability

while driving through curves. ATC utilizes Engine

Torque Limiting where the ECU communicates with

the engine’s controller and/or Differential Braking

where individual wheel brake applications are used

to improve vehicle traction.

Premium ECUs have a drag torque control feature

which reduces driven-axle wheel slip (due to driveline

inertia) by communicating with the engine’s controller

and increasing the engine torque.

ESP

Electronic Stability System

The ESP

functionality of the Bendix Advanced ABS

system responds to a wide range of low- to high-

friction surface scenarios including rollover, jackknife

and loss of control. It is the recommended system for

all power vehicles and especially critical for tractors

pulling trailers. In the case of vehicle slide (over-steer

or under-steer situations), the system will remove the

throttle and then brake one or more of the “four corners

of vehicle” (in addition to potentially braking the trailer),

thus applying a counter-force to better align the vehicle

with an appropriate path of travel. For example, in an

over-steer situation, the system applies the “outside”

front brake; while in an under-steer situation, the

“inside” rear brake is applied.

In the case of a potential roll event, the system will

remove the throttle and quickly apply the brakes to

slow the vehicle combination below the threshold.

Trailer ABS

See the section beginning on page 41 for more

information on trailer ABS systems and components.

Antilock Braking Systems

90° Speed

Sensors

Straight Speed

Sensors

Sensor

Clamping

Sleeve

Bendix

WS-24

™

Wheel Speed Sensors

Bendix

M-32

™

and

M-32QR

™

Modulators

Delivery

Supply

Exhaust

Electrical

Connector

M-32QR

™

Modulator

M-32

™

Modulator

Supply

1 2 ... 32 33 34 35 36 37 38 39 40 41 42 ... 69 70

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