Iveco Stralis AT/AD. Manual - part 242

In a dynamic situation the effect on the vehicle will be managed in this way:

Figure 22

Ca. Front axle load — Cp. Rear axle load — Cr. Load on fifth wheel — Da. Front axle braking force —

Dp. Rear axle braking force — Dm. Braking force at graduated release — Ds. Semitrailer braking force —

Ffa. Resultant of braking/front axle load — Ffp. Resultant of braking/rear axle load — Ffm. Resultant of braking/load

at graduated release — Ffs. Resultant of braking/semitrailer load — a. Braking angle — Rr. Reaction on the fifth wheel —

Dec. Required deceleration — g. Acceleration due to gravity — z. Braking ratio

Generally, the EBS will tend to apply a braking force in proportion to the load on the axles, that is to maintain the same angle ”á”
for all the axles:

Ds (Dm)

Cs (Cr)

= Tag

 α =

dec

= z

This, as may be seen, also holds for the semitrailer control.

77208

TRALIS

AT/AD

AIR SYSTEM - BRAKES

Base - January 2003

If the reaction on the fifth wheel ”Rr” is not as expected, the system automatically increases or decreases the predominance at the
graduated release and ”Ffm” accordingly so as to ensure the best compatibility between the tractor and semitrailer in compliance
with current type-approval standards, as may be seen in the following compatibility diagram.

000987t

Figure 23

AUXILIARY BRAKE INTEGRATION

Commercial vehicles are normally fitted with auxiliary brakes for slowing down without causing wear, such as the exhaust brake and
intarder.

On vehicles equipped with the EBS, these devices can be integrated to ensure the vehicle slows down sooner and more effectively.
The exhaust brake/intarder action percentage is set by the driver with the lever.

The exhaust brake will be applied up to a speed of 1000 rpm, while the action of the retarder will cause the following action depending
on the position of the lever:

001685t

Figure 24

Position 0 — disengaged

Position 1 — E.B. 100%

Position 2 — E.B. 100% + Intarder 25% (20% *)

Position 3 — E.B. 100% + Intarder 50% (40% *)

Position 4 — E.B. 100% + Intarder 75% (60% *)

Position 5 — E.B. 100% + Intarder 100% (80% *)

Position 6 — E.B. 100% + Intarder 100%

These applications, always possible, will be signalled to the driver by the relevant indicator lights coming on.
*

Vehicles with mechanic gearbox.

On vehicles without the optional Intarder, the auxiliary brake lever has just three positions: off, E.B. 50%, E.B. 100%.

On vehicles fitted with a EuroTronic gearbox, with the auxiliary brake lever on position 6, slowing down will be more
effective with the automatic gear shift down.

AIR SYSTEM - BRAKES

TRALIS

AT/AD

Switching the engine off for longer than one minute involving a change in load, tyres or ratios at the rear axle causes the adjustment
data to be lost and so a fresh period of data acquisition will be necessary for the system to be able to reactivate auxiliary brake
integration if no vehicle parameter is changed the integration will be immediately available.

If manually activating the auxiliary brakes, the next time the brake pedal is pressed will implement integration.

On releasing the brake pedal, if the manual action is compatible with the calculated action it will be kept active.

If activating the auxiliary brakes, both manual and integrated, causes the rear axle to slow down too much and a tendency for it
to lock, the EBS control unit, on detecting this situation via the speed sensors, will immediately disengage them or turn on the
auxiliary brake Slip Control.

- Prevents the wheels locking when the vehicle is braking, no matter what grip is available on the road.

- Shortens stopping distances.

- Provides safety for the driver who can keep the vehicle’s stability and direction.

EBL function controls rear axle wheel “skidding” by comparing it to front axle wheel speed.
On the basis of wheel r.p.m.’s and braking pressure (detected by the sensor upstream from rear axle ABS modulators), the central
unit calculates vehicle speed, rear axle wheel “skidding” and minimum acceleration expected.

“ABS-EBL” SYSTEM (ANTI-LOCK BRAKE SYSTEM — ELECTRONIC BRAKE LIMITER)

“ABS” (Anti-Lock Brake System)

The braking of a moving vehicle and the according deceleration and stopping distances depend above all on the grip between the
surfaces of the tyres and the road.

With a fully efficient braking system, a further improvement in braking can only be achieved by acting on the friction of the tyres
or on the grade of the road surface.

Even in these optimum conditions, absolute braking safety is anyhow not guaranteed when faced with especially tricky situations,
such as poor grip due to a wet or icy road surface: the driver is forced to moderate use of the brakes in order to avoid partially
locking one or more wheels, with the risk of skidding dangerously.

The function of the ”ABS” is therefore to ensure vehicle stability (in all braking conditions), preventing the wheels from locking
irrespective of the state of the road surface, so as to ensure the available grip is made full use of.

Even in the case of emergency braking, the system makes it possible to keep direction, that is to turn the steering wheel to avoid
obstacles with no risk of skidding.

In short, the anti-lock brake system (ABS):

TRALIS

AT/AD

AIR SYSTEM - BRAKES

Base - January 2003

FRONT AXLE

braking pressure

The EBL function checks the rear axle wheel ”slip”, comparing it with the speed of the wheels of the front axle.

The control unit input data are the wheel speed and braking pressure measured by the pressure sensor installed upstream from
the rear axle ABS modulators.

On the basis of these values, the control unit calculates the speed of the vehicle, the vehicle’s deceleration, the rear axle wheel ”slip”
and the minimum deceleration contemplated.

The EBL function is activated (the rear ABS modulators maintain the set pressure) when the driver applies an excessive braking
force for the conditions of load on the vehicle, in short when the rear axle slip and vehicle deceleration thresholds are exceeded.

Operating Logic

The purpose of the electronic control unit is to slow down the vehicle as quickly as possible, ensuring its stability and avoiding the
tendency for the wheels to lock.
To achieve this aim, while braking, the electronic control unit will be informed of the:

- braking intensity required by the driver via the rear axle pressure sensor,

- reaction on slowing down due to the pressures made available via the speed sensor signals.

The continuous monitoring and processing of this information, in relation to the set aim, will cause the rear axle modulating valves
to activate appropriately and optimize the braking action accordingly.

REAR AXLE

braking pressure

Braking

action

Braking intensity request

Wheel speed

CONTROL UNIT

AIM

∆ Slip = 0

Figure 25

AIR SYSTEM - BRAKES

TRALIS

AT/AD

EBL (Electronic Brakes Limiter)

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