Base Plate

10

605_028

Passive Systems
Additional Outlet Orifices Close

Distributor Housing

As long as Driver Airbag Igniter 2 N250 has not been
activated, the additional outlet orifices in the distributor
housing are sealed by the control ring.
The gas from the gas generator flows through the upper
orifices in the distributor housing and directly into the
airbag. A retaining clip holds the control ring in its rest
position, preventing unwanted rotation of the control
ring.
Igniter 2
Control Ring

Retaining Clip

Base Plate

605_029

Additional Outlet Orifices Open

Distributor Housing

Depending on impact severity and the driver's seating
position, the Airbag Control Module J234 decides when
to activate the N250.
When N250 is ignited, the resulting gas pressure
displaces a pin which rotates the control ring. The
additional outlet orifices in the distributor housing are
opened.
A portion of the remaining gas from the gas generator
can now be released directly into the atmosphere.
The gas from the airbag can also escape into the
atmosphere through the orifices in the distributor
housing. This prevents the airbag from inflating further,
and ensures the airbag is "adapted" to the occupant’s
seated position.

Pin
Control Ring

Igniter
Igniter2 2

Pin

Retaining Clip
Retaining clip

Base plate

605_030

11

Passive Systems
Adaptive Driver’s Airbag Gas Generator — Version 3
The Driver Airbag Igniter N95 activated by Airbag Control
Module J234 and ignites the priming charge which in
turn ignites the actual propellant charge. If the gas
pressure resulting from ignition of the propellant charge
is high enough, a tab opens the outlet orifices. The gas
is now able to flow freely through the metal filter into
the airbag. The airbag unfolds and is inflated.
An additional igniter for airbag adaptivity, Driver Airbag
Release Valve Igniter N490, is attached to the back of
the airbag module. The airbag also has an extra snoutlike outlet orifice.

The igniting propellant charge inside the airbag keeps
this outlet orifice closed. Depending on the impact
severity and the driver's seating position, J234 activates
the driver airbag relief valve igniter, severing the metal
band.
As a result, the additional outlet orifice opens. The
airbag is "adapted" to suit the occupants in a manner
appropriate to the situation.

Priming Charge

Propellant Charge
Foil

Igniter
N95

Metal Filter

605_031

Fastening Bolt

Igniter N95

Outlet Orifice

Fastening Bolt

Band
Igniter N490

605_032

12

605_033

Passive Systems
Front Passenger Airbag Gas Generator
This gas generator is a hybrid gas generator. Airbag
Control Module J234 activates the Front Passenger
Airbag Igniter 1 N131. The activated igniter breaches
the rupture disc 1 and ignites the propellant charge.

The combustion of the propellant charge causes the
pressure inside the compressed gas cylinder to increase
until rupture disc 2 breaks. The gas mixture unfolds and
inflates the airbag.

Propellant Charge
Spring

Igniter

Rupture Disc 1

Rupture Disc 2
Compressed Gas Cylinder
605_034

13

Passive Systems
Adaptive Front Passenger Airbag Gas Generator — Version 1
This is a hybrid gas generator with a second outlet orifice. This type of gas generator allows the passenger airbag to be
filled to different degrees.
Airbag Control Module J234 determines the time interval between activation of both igniters based on impact severity
and the passenger's seating position.

Compressed Gas Cylinder

Priming Charge

Igniter 2

Igniter 1

Propellant Charge

Rupture Disc 1

Rupture Disc 2
605_035

The priming charge, which is ignited by igniter 1, ignites the actual propellant charge. The pressure inside the compressed
gas cylinder increases until rupture disc 1 bursts at a certain pressure. The gas mixture inflates and unfolds the airbag.

Priming Charge

Igniter 1

Propellant Charge
Rupture Disc 1

605_036

The Airbag Control Module J234 ignites igniter 2 after a defined period of time. A targeted pressure pulse from igniter 2
causes rupture disc 2 to burst.
A portion of the remaining gas from the compressed gas cylinder now vents into the atmosphere and bypasses the
airbag.

Rupture Disc 2
Igniter 2

605_037
14

Passive Systems
Adaptive Front Passenger Airbag Gas Generator — Version 2
The Airbag Control Module J234 activates the Front Passenger Airbag Igniter 1 N131. The flame of igniter 1 ruptures
disc 1 and ignites the priming charge, which in turn ignites the actual propellant charge.
The combustion of the propellant charge increases the pressure in the compressed gas cylinder until rupture disc 2
breaks. The gas mixture unfolds and inflates the airbag. The adaptability function on the passenger side is similar to
that on the driver side.

Rupture Disc 2

Rupture Disc 1

Priming Charge

Propellant Charge
Compressed Gas Cylinder

Igniter 1 N131

605_038

Hybrid Gas Generator

Igniter 1 N131

605_039

Igniter N491

15

Passive Systems
Side Airbags
The side airbag modules are specific for each Audi model.
The latest-generation side airbag modules are known as
"Soft Cover Modules".
In these modules, a textile casing replaces the plastic
shell enveloping the entire airbag module. The soft
surface of the textile casing integrates into the seat.
It is also lower in weight.

Side Airbag Unfolds

605_040

Head-thorax airbags are used in some Audi models such
as the Audi A5 Cabriolet. Since a curtain airbag will
not be present when the top is in the open position,
there must be some means to protect occupants in side
collisions.

Head-Thorax Airbag Unfolds

This airbag module is designed to protect not only the
head, but also the body of the occupants.
The airbag module is integrated into the backrest of each
of the front seats. This ensures proper positioning of
the airbag in relation to the occupants, regardless of the
seat adjustment.

605_041

16

Passive Systems
Gas Generator For Side Airbag
The side airbags use various pyrotechnic solid propellant generators.

Version 1
Propellant Charge

Igniter

Priming Charge

Metal Filter

605_042

Version 2
Igniter

Propellant Charge

Metal Filter

Priming Charge

605_043

Version 3
Igniter

Rupture Disc 1

Priming Charge

Propellant Charge

Rupture Disc 2

Spring

Metal Filter

605_044

Airbag Control Module J234 energizes the corresponding side airbag igniter. This ignites the priming charge that will
ignite the actual propellant charge. The developing gas, which is purified and cooled by the metal filter, unfolds and
inflates the airbag.
17

Passive Systems
Side Curtain Airbags
The side curtain airbags are installed on the left and right hand sides behind the headliner. Hybrid gas generators are
used to inflate the curtain airbags. The curtain extends from the A pillar to the D pillar, covering almost the entire side
window area. The curtain airbags help provide occupant protection in the event of a side impact. The position of the gas
generators can vary depending on model.
Gas Generator

605_045

Version 1
The igniter is activated. The gas pressure produced in the igniter displaces a piston, which in turn shears off the
rupture disc. The compressed gas emerging from the cylinder can flow into the airbag. The airbag unfolds and is
inflated. With these gas generators, the pyrotechnic igniters have only the task of opening the compressed gas
cylinder.
Igniter
Rupture Disc
Piston

Filter
Compressed Gas Cylinder

605_046

Version 2
The compressed gas cylinder igniter is activated by the Airbag Control Module J234, igniting the priming charge. The
combustion of the priming charge produces a gas pressure which causes rupture disc 1 to burst. The gas pressure travels
through the compressed gas cylinder and causes the rupture disc 2 to burst. The gas mixture flows through the filter
and into the airbag.

Igniter

Propellant Charge

Rupture Disc 1

18

Filter

Compressed Gas Cylinder

Filter

Rupture Disc 2

605_047

Passive Systems
Front Belt Retractors
Pyrotechnic Safety Belt Tensioner —
Safety Belt Tensioner

Electrical Plug Connection

A metal band is wound around the belt retractor shaft.
Both open ends of the band are connected to the belt
retractor shaft. The closed end is looped around the
safety belt tensioner igniter.

Igniter

Belt Retractor Shaft

Metal Band

605_048
Metal Band Loop

When Airbag Control Module J234 ignites the safety belt
tensioner igniter, the pressure causes the loop of the
metal band to expand.

Electrical Plug Connection

The movement of the metal band pulls on the belt
retractor shaft rotates to tension the safety belt.
Igniter

The retractor stops tensioning the safety belt when the
counterforce on the belt is greater than the force exerted
by the safety belt tensioner.

Belt Retractor Shaft

Metal Band

605_049
Metal Band Loop

19

Passive Systems
Adaptive Belt Force Limitation
In models with adaptive airbag systems, the front belt
retractors have an adaptive two-stage belt force limiter.

Sliding Element

Igniter

In the event of a collision, the safety belt tensioners
(band tensioners) are ignited first. The safety belt
tensioner retracts the safety belt as far as possible. The
belt retractor blocks the belt retractor shaft, preventing
the safety belt from unreeling, controlling the forward
motion of the occupants. If the occupant moves further
forward, the belt force limiter permits controlled
unreeling of the safety belt at a certain force level.

Torsion Shaft 2
Gear 2

Belt Retractor Shaft

Gear 1

605_050

Both shafts of the retractor system are torsion-type
shafts. They are coupled together by gears.

Torsion Shaft 2
Rotates

Sliding Element

Sliding Element Decoupled
Gears 1 and 2

Gear 2

Gear 1

Belt Retractor Shaft
(Belt Retractor Shaft Rotated)
605_051

The Airbag Control Module decides when to activate the
belt force limiter igniter depending on impact severity
and seating position.
The second torsion shaft is decoupled from the belt
retractor shaft. The belt retractor shaft now counteracts
the force that the safety belt exerts (low force).
The safety belt tensioning function, the belt force
limiting function and the front airbags are coordinated
to help ensure the protection of the occupants.
The belt force limiter igniters are not activated in the
event of a side impact or rear collision.

Igniter

605_052

Sliding Element

Torsion Shaft 2

Gear 2

Belt Retractor Shaft
Gear 1

605_053
20

Passive Systems
Front Belt Retractors In Combination With Audi pre sense
If the vehicle is equipped with the Audi pre sense
system, the following functions are integrated in the
front belt retractors:

•• Reversible safety belt tensioner with control unit
•• Pyrotechnic safety belt tensioner
•• Adaptive belt force limiter
Reversible Safety Belt Tensioners
Front Left Safety Belt Tensioner Control
Module J854 and Front Right Safety Belt

Safety Belt Tensioner
Control Unit

Electric Motor

Active Belt Force
Limiter

Tensioner Control Module J855
The Front Left and Right Safety Belt Tensioner Control
Modules J854 and J855 are networked using an extended
CAN bus and the Data Bus On Board Diagnostic Interface
J533. The safety belt tensioner control modules activate
the reversible safety belt tensioning motors.

There different force levels are available depending on
the situation:
1. Low force level = belt slack reduction
2. Medium force level = pre-tensioning
3. High force level = full tensioning

Pyrotechnic Safety Belt
Tensioner

605_054

Gear Drive

Hook

In addition:
Driver Plate

In the event of a head-on collision, Airbag Control
Module J234 decides, based on the severity of the
impact, which safety belt tensioners will be activated.
(pyrotechnic or reversible).

Hook

605_055

At this point, J234 sends a data signal. J854 and J855
initiate the correct tensioning of the safety belts based
on the data signal received.
The driving plate is driven via a gear drive when the
electric motor begins to rotate. Two extending hooks
connect the driving plate to the belt retractor shaft, and
the safety belt is retracted.
If the electric motor stops or reverses slightly, the hooks
are able to retract again and release the belt retractor
shaft.

Hook
Hook
Driver Plate

605_056
21

Passive Systems
Front Pyrotechnic Belt Tensioners Combined With Audi pre sense
These pyrotechnic safety belt tensioners have a rack-andpinion design.
Damping Element

The signal from Airbag Control Module J234 ignites
Driver/Passenger Safety Belt Tensioner Igniter 1 N153
and N154. The pressure causes the piston coupled to
the rack to move upwards. The rack turns gears 1 and 2
via the pinion.

Gear 1
Pinion

Gear 2
Freewheel Outer Ring
Belt Retractor Shaft
Roller
Piston With Rack
Igniter 1

605_057

Gear 2 is part of the outer ring of the belt retractor shaft
freewheel. When the outer ring turns, the rollers are
thrust inwards until they lock into place between the
outer ring and the belt retractor shaft. The rotational
movement is now transmitted to the belt retractor shaft,
and the process of retracting the safety belt begins.

Position of the Rollers on
Engagement of the Outer
Ring and Belt Retractor Shaft

The retractor stops tensioning the safety belt if the
counterforce acting on the safety belt is greater than the
force exerted by the safety belt tensioner.

Rollers in Starting
Position

605_058
22

Passive Systems
Adaptive Belt Force Limiters In Combination With Audi pre sense
The front belt retractors have two-stage belt force
limiters. In the event of a head-on collision that meets
the conditions for deployment, the pyrotechnic belt
tensioners are ignited first. The locking mechanism
locks the belt retractor shaft and prevents the safety belt
from unreeling, which would occur due to the forward