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Seat belt 3.1 History and Function of Seat Belt 3.2 Types of Seat Belt 3.3 Point Seat Belt Detail 3.4 ELR Emergency Locking Retractor 3.5 WLR Webbing Clamp Locking Retractor 3.6 Pretensi

SRS AIR BAG

(Supplemental Restraint System)

1 What is A/Bag?

1.1 Necessity

1.2 Purpose

1.3 Effect

1.4 History of Air Bag

1.5 Air Bag System Category

2.4 PAB (Passenger Air Bag)

2.5 SAB (Side Air Bag)

2.6 CAB (Curtain Air Bag)

3 Seat belt

3.1 History and Function of Seat Belt

3.2 Types of Seat Belt

3.3 Point Seat Belt Detail

3.4 ELR (Emergency Locking Retractor)

3.5 WLR (Webbing Clamp Locking Retractor)

3.6 Pretensioner

3.7 Load Limiter

3.8 Troubleshooting of Seat Belt

4 Sensor

4.1 PPD (Passenger Presence Detection)

4.2 OCS (Occupant Classification System)

4.3 PODS (Passive Occupant Detection System)

4.4 FIS (Front Impact Sensor)

4.5 SIS (Side Impact Sensor)

5.4 Inside Sensors and Etc.

5.5 Diagnostic Troubleshooting Flow Chart

1 What is A/Bag?

1.1 Necessity

The seat belt is a concrete device for protecting the body of a passenger in a collision But when the body is subjected to a large impact in the case of a high-speed collision, the seat belt alone cannot protect the body

And especially in the case of a serious front-end collision, the upper body tilts forward even when it is secured with the seat belt, and the head or chest may collide with the steering wheel or the

windshield, resulting in injuries

The SRS Air bag System is a device that reduces head and chest injuries to the driver and

passengers by inflating an air bag installed in the steering wheel or the instrument panel when such a collision occurs, supplementing the function of the seat belt

Thus, the SRS Air bag System is the supplements the restraining and protective functions of the seat belt For that reason the name of the system was chosen as the acronym of Supplemental Restraint System

1.2 Purpose

Functions of Air Bag

• Absorbs kinematics energy of occupants

• Protects occupants from interior trims

• Protects occupants from broken glass

• Reduces occupants neck load by kinematically restraining spin of neck

1.3 Effect

Effect of Safety System

• Decrease in Fatality when Safety System is used (Data published by NHTSA, 1999)

• When only using Seat Belt: 45% Decrease

• When only using Frontal Air Bag : 14% Decrease

• When using Seat Belt + Frontal Air Bag : 50% Decrease

1.4 History Of Air Bag

1998: Transportation Equity Act for the 21st Century enacted by Congress [TEA 21] - for advanced air bags.

1993: First of 23 deaths over three years caused by passenger air bags: Diana Zhang, 6, of Canton, Ohio.

Car companies required to begin phasing in passenger air bags in cars and light trucks.

1991: President Bush signs a law requiring an air-bag phase-in starting the '94 model year Deadlines for passenger

air bags: all 1998 model year cars; all 1999 model year trucks [ISTEA :: Intermodal Surface Transportation Efficiency Act]

1990: First report of a driver being killed by an air bag: 64-year-old women suffers fatal chest injuries from air bag.

1989: Ford announces driver air bags will be standard equipment in nine car lines.

1988: In a dramatic turnaround from CEO Iacocca's previous anti-bag position, Chrysler becomes the first U.S

automaker to install driver air bags as standard equipment in all its domestic-made cars.

1987: NHTSA lets automakers use driver air bags to meet passive-restraint requirements until '94 model year.

1986: NHTSA allows automakers to meet passive-restraint requirements through the 1990 model year with only driver

air bags The agency cites concerns about the dangers of passenger air bags.

1984: Now Chrysler CEO, Iacocca lambastes air bags as example of "solution being worse than the problem."

1983: The Supreme Court rules against the Reagan administration and directs NHTSA to review the case for air

bags.

1981: Under the anti-regulatory Reagan administration, NHTSA announces one-year delay of passive-restraint rule,

proposes that it be rescinded altogether [Transportation Secy: Elizabeth Dole]

NHTSA cancels passive-restraint standard, citing uncertainty about public acceptance and use of automatic safety belts.

1979: General Accounting Office warns that out-of-position occupants are in danger from air bags.

General Motors notifies NHTSA it will not offer optional passenger air bags on 1981 models as planned

because of "potential for risk of injury to unrestrained small children who would otherwise survive an impact without significant harm." NHTSA chief Joan Claybrook insists "the trade-off in terms of saving thousands of lives clearly outweighs these extraordinary and infrequent risks."

1977: Carter administration Transportation Secretary Brock Adams announces that all new cars sold in the USA must

have front air bags or passive safety belts that fasten without any effort by the driver or passenger by the 1984 model year.

1976: Transportation Secretary William Coleman says air bags in all cars would save about 12,000 lives each year

Scraps passive-restraint requirement when automakers pledge to install some air bags voluntarily.

1975: Volvo report says eight of 24 pigs used to simulate effect of air bags on unrestrained children were killed by the

force of the air bags All but three pigs were seriously injured.

1974: GM starts making some dual air-bag-equipped Cadillacs, Oldsmobiles and Buicks, hoping to sell 100,000 a

year Drops effort three years later after selling only 10,000.

1973: General Motors manufactures 1,000 Chevrolets equipped with experimental air bags and provides them to fleet

customers for testing.

Infant, unrestrained on passenger seat of one of the experimental Chevrolets, is killed when a passenger bag deploys in a wreck GM considers that the first air-bag fatality.

An Oldsmobile Toronado, first car with a passenger air bag intended for sale, rolls off assembly line.

1971: Ford builds experimental air bag fleet.

NHTSA delays passive-restraint mandate until 1976 after Henry Ford II, Ford President Lee Iacocca lobby President Nixon.

1970: National Highway Traffic Safety Administration (NHTSA) orders passive restraints by 1974 model year.

1969: Nixon administration proposes passive restraints in cars to protect unbelted occupants.

General Motors warns federal safety officials that children too close to an inflating air bag could be "severely injured or killed."

1966: President Johnson signs the National Traffic and Motor Vehicle Safety Act, which requires the government to

come up with safety standards for new vehicles Previously, auto safety had been largely unregulated.

1.5 Air bag System Category

It is not necessary to classify Air Bag in terms of system, because Air Bag has been developed gradually In the past, the sensor was mechanical, whereas now it is electronic Of course, there is a difference of ACU depending on the manufacturers such as Siemens, Hyundai Air Bag (HAE), TRW, and Delphi Mando Presently, there are two types: a sensor may be installed inside the ACU, or it may

be located outside

1) Single Sensor Type (Intergrated Type with sensor in Air bag control module)

Inside the ACU, there is a sensor that measures the impact from the front and left side, right side

2) Multi-Sensor Type (Front sensor Type)

Inside the ACU, there is a sensor that measures the impact from the front and left side, right side By comparing the impact between the sensor in the front and the inside, Air bag deployment is decided

Location of Sensors – FIS is located at the rear body of the Front Bumper, and selects both left and right side SIS is located in the bottom of Center filler (usually beside the BPT), and is used for the deployment of SAB and CAB.

A sensor that can sense the impact from the front and left, right is installed inside the ACU Most of the sensors used at Hyundai motor presently are electronic type, whereas only the Safing sensor located inside the ACU is mechanical type

These sensors are not compatible each other Besides, all sensors are direction-oriented, so be careful when installing Especially, when installing, if slope or direction is wrong, the deployment of Air bag maycause big trouble

1.7 Basic Principle

Operating Sequence

The operation of the Air bag depending on time is as follows

105 mSec ~ 150 mSec

Vent Gas (Bag Deflation)

Airbag System Completed

20 mSec

35 mSec

40 mSec

Bag Deploying

Ignite the Inflator

Full Deployment of the Bag

Produce Nitrogen Gas to Inflate the Bag

Protect the Occupants

3 mSec

Crash

Crash Sensing

Make decision deployment or undeployment

2.1 DAB (Driver Air Bag)

The driver module sits centrally as a complete unit in the steering wheel At high speeds, the danger arises of being thrown against the steering wheel in the event of a crash, even if the driver’s seat belt

is fastened

The air bag protects the driver against collision with the steering wheel and thus alleviates the

consequences of the accident

The compact cup-shape generator, the air bag, the cover and the necessary installation andconnection components comprise the air bag unit on the driver’s side

The tightly folded air bag allows the space requirement of the driver module to be kept at a low level The air bag has a volume of approx 40 ~ 60ℓ

After the air bag system is ignited, the cover is ripped open at a pre-determined rip seam and clears the way for the air bag, which is inflated by the gas flowing into it All electrical connections and leads are equipped with shorting bar to protect against erroneous ignition(Deployment)

1) DAB (Driver Air Bag)

Recently some drivers have been injured due to Air bag deployment, so now DAB employs a

depowered type of Air bag Nevertheless, small drivers(below 150cm) may be injured by Air bag deployment

Steering WheelMulti Function Switch

Depowered Air bag

March 1997, NHTSA in U.S.A announced that vehicle manufacturers can depower (reduce the inflation pressure) all air bags so that they inflate less aggressively

 Depowering of 20 to 35 percent of the severity (inflator)

 Purpose of ensuring the female and child

 To protect the neck

Therefore, these days the Dual Stage Air bag module has been developed that is safer than the depowered type In the case of vehicle collision, there may be various intensity levels of impact, but simply three stages can be considered A basic Air bag is designed to inflate at a constant pressure and velocity irrespective of the intensity of collision impact Consequently, in case of a lower speed collision, Air bag sometimes resulted in injuries It is now required to design an Air bag that can be deployed at different pressures and velocities depending on the collision impact Dual Stage Air bag can solve this problem In order to adjust the velocity and pressure, at which the Air bag inflates, in three stages, two Igniters are installed in the Air bag Module

Considering the pressure and velocity at which all Air bag deploys to be 100%, the pressure and velocity of the 1st Igniter is adjusted to be about 70% 2nd Igniter is adjusted to be about 30% Through several collision tests, the above 70:30 ratio can be adjusted For example, for a lower speed

collision, 1st Igniter only deploys And for middle speed collision, 1st Igniter deploy and 2nd Igniter deploy within 10ms too For a much higher speed collision, 1st and 2nd Igniter together deploy

By adjusting the pressure and velocity at which an air bag deploys according to the collision intensity, the safety of the driver can be secured Recently, in order to secure much safety, when an Air bag deploys, it considers the information on whether driver wears seat belt, or where the driver’s seat is located, etc

Advanced air bags

Advanced frontal air bags are designed to meet the needs of the occupant in a variety of specific

crash situations Depending on design, advanced frontal air bag systems automatically determine if and with what level of power the driver frontal air bag and the passenger frontal air bag will inflate

The appropriate level of power is based upon sensor inputs that can typically detect (1) occupant size,(2) seat position, (3) seat belt use of the occupant, and (4) crash severity Some systems also use the

occupant’s distance from the air bag as an additional input.

1) Necessity

Advanced frontal air bag systems are designed to be even more effective than current air bags (also known as “depowered” air bags ) in saving lives, while at the same time reducing the potential of causing an air bag induced serious injury or death

Some earlier generation air bags have been known to injure or kill, both adults and children, who were seated too close to the driver or right front passenger airbag when it deployed

“Too close” can occur when an occupant, typically unbelted or leaning out of position, is thrown forward just before the crash impact (the period known as pre-crash braking) to within

a few inches of or directly on top of the rapidly accelerating air bag NHTSA estimates as of June 2003, 231 people (144 children and 87 adults) have lost their lives in such incidents

Advanced frontal air bags were designed primarily to minimize the risk of an air bag related injury or death to children and small-statured adults In crashes

where a higher-powered air bag deployment would not be necessary and/or could cause injury, such as in a low-speed crash or in a crash where the occupant is leaning out of position, the system reduces the risk of an air-bag injury by either 1) shutting off (suppressing) the frontal air bag or 2) by deploying the frontal air bag with less inflation force

(2) Dual stage (Advanced Air Bag)

3) DAB Module (Single-General)

2.2 Clock Spring

The clock spring forms the electrical connection between the A/Bag control unit and the driver module

in the steering wheel

The clock spring guarantees the electrical connection in every steering wheel position

Before installing or removing the clock spring the front wheels are to be set in straight-ahead position, and the clock spring must not be twisted when it has been removed, in order to prevent a fault occurring in the clock spring.

When replacing a new Clock Spring, be sure to check the accurate position of the tape or clip that prevents turning its inner coil spring, and remove it before installing If not working in the said

conditions, Clock Spring may be cut off during driving If a worker disassembled the Clock Spring, make two frontal wheels(tires) towards the front first, and keep turning the Clock Spring in one

direction will rotate 6.5 to 7.5 cycles Then, turn about 3 to 3.5 cycles in the converse direction,

aligning the triangle mark on the Clock Spring surface Assemble to this condition

2.3 Inflator

Inflator Assembly

Let’s consider Pyrotechnic Inflator used recently In the past, various types such as compressed air type and Pyrotechnic Type have been used, but recently Pyrotechnic Inflator has been used due to itscredibility, endurance and simple installment Looking at the inner structure, when the current flows in the 5th Initiator, in other words when supplying the current specified from the ACU, the Initiator first make a small explosion, then ignites 2nd Auto Ignition Charge The ignited heat activates the 6th Gas Generator, producing the gas instantly At this time the heat occurred is very high, dusts are

generated

Therefore, the heat of this gas is lowered and its dust is removed when passing through the 4th Filter This gas fills the Air bag to inflate The major components of this gas are He N2,CO2,Ar The inner structures of DAB, PAB, and SAB, etc are very similar to this The Passenger Module is positioned inplace of the glove box in the dash board(crash pad)

2.4 PAB (Passenger Air Bag)

The Passenger Module is positioned in place of the glove box in the Dashboard

There are two ways to install PAB : One is to install it inside the Dashboard, and the other is to install from the outside When installing in one assembled Dashboard, the appearance of the Dashboard is clean and looks good, but when PAB deploys, the outside of the Dashboard should be replaced The later type –separable one- doesn’t look good, but when deploying, only the separated PAB part can

Warning label Inflator assembly

Connector

PAB is to protect the passenger in the front passenger seat when a collision occurs Since PAB should protect wider area, its volume is 120~160ℓ It may be dangerous if cellular phone or other objects are attached to deployment area When Air bag deploys, these objects may injure the

passenger

1) Air Bag Firing Sequence

The firing circuit for the inflator will be activated in the following sequence for deployment (If is the instant at which the deployment decision is made)

The time to deploy the Air bag is so short, so in order to fill the Air bag by generating so much gas within the time, big sound of noise (explosion sound) occurs It is usually over 100dB

When the Driver Air Bag and the Passenger Air Bag deploys simultaneously with this noise, it may damage the human ear drum Therefore, Air bag deployment occurs in the DAB 1ms in advance It may decrease noise and delay the pressure increase inside the car

50 ms Td=1ms

Tf

ON OFF

PAB

DAB

ON OFF

2.5 SAB (Side Air Bag)

Side air bag have been developed to help reduce injuries thorax associated with some side impact crashes, and could mean the difference between just a headache and almost certain death

They are designed to produce energy-absorbing buffers between people and the vehicle doors that can be driven into them in side impacts

They can be mounted in seats for thorax or head/thorax protection

When thorax Air bag(side Air bag) comes to side impact crashes, thorax bags are estimated to reducethe risk of serious chest injury by approximately 20%

Sending Signal to SRSCM

Crash

SRSCM operates FSABImpact Sensing

2.6 CAB (Curtain Air Bag)

The Curtain air bag module offers significantly enhanced head and neck protection for drivers

The rollovers are a significant cause of serious injury, especially to the head and neck So the curtain air bag module offers drivers and passengers advanced added protection

The curtain air bag module deploys from a vehicle’s roof rail and may be used in combination with other side impact air bag system for added torso protection

The curtain air bag module delivers protection during multi-impact situation common to the vehicle rollovers

8590

593

10866

577 0

2000 4000 6000 8000 10000 12000

Head Injury Criterion

Without CAB With CAB

HIC can be reduced by approximately 80%

Curtain air bag maintains the inflation state of the Air bag over 6 seconds to prepare for the possible collision at the vehicle side in addition to various complex impact and vehicle turnover When the vehicle collision occurs at the side, it prevents the passenger from taken out.

ROLL TYPE OR FOLD TYPE

CURTAIN AIR BAG

INFLATOR

CAB: Located at Roof Rack, and moves downwards when deployment occurs.

3 Seat Belt

DRIVER BELT

3.1 History and Function of Seat Belt

1) 2 Point Static Belt (about 1922)

Belt whose webbing length is adjusted by the length adjuster without retraction function(Used in BUS)

2) NLR (None Locking Retractor, 1965∼) :

Since it only winds Seat belt without locking function, use after taking out Seat belt completely

Usually the seat belt installed in the passenger seat in the bus is NLR type

3) ALR (Auto Locking Retractor, 1970∼)

Due to Auto Locking function, the length of seat belt is automatically adjusted However, after seat belt is locked once it is taken out, it no longer would not be taken out, and returns to the original place when locking function is removed (Disadvantage: pressure in passenger’s chest area)

4) ELR (Emergency Locking Retractor, 1972∼)

When vehicle collision occurs or under emergency situation, the belt is locked and would not be takenout any more This is the type used these days

(1)T/R (Tension Reducer)

Device to reduce tension occurred due to Rewinding Spring Force (Solenoid) When wearing, this function allows to reduce tension, by using two kinds of Rewinding Spring with the different Return Force with the sensor that detects wearing and no wearing

(2)WLR (WEBBING Locking Retractor)

When the vehicle collides and under emergency situation, belt is locked and it is rewound by using the force of the explosion, protecting the passenger safer

(3)CLR (Convertible Locking Retractor)

Developed to safely fasten CHLD SEAT By law, required to install in North America It is activated by Gear and Cam, and if all of the belt is pulled out, ALR begins to be activated, and after a certain amount of Webbing is wound, it returns to ELR again

Legalization of Seat Belt

The seat belt which has been developed since 1950s intended to legalize the installation after 1960s but the resultant was so low, however, the legalization of a fastened seat belt had been realized after 1970s

Regulation of a seat belt -1968 : FMVSS 208 in USA

1969 : ADR 5A in Australia

1977 : EEC No 14 in EuropeObligation of a seat belt

Obligated an attachment portion

for a child seat

Krone

Germany regulation

Crash Features & Occupant Injuries

When a car strikes against structure and other car, we called as a first collision, and then an occupant

in a car collide with interior structure in a car, this is called as a second collision

If a car bumps a barrier in a frontal direction,

V0 : a velocity before a collision into a barrier

L1: a deformation amount of a body with absorbing an crash energy

t: a time after a first crash

V(t): a body velocity at t time after a first crash

Vp(t): a relative velocity between an occupant and a vehicle at t time

That is, a velocity of causing second collision at t time goes

In the event of crash, the allowable space regarding a deceleration of an occupant is L1 + L2

When a car bumps a structure and other vehicle in a frontal direction, a collision sequence occurs continuously

• 1st Collision : a car crash itself

Vp(t) = V0 - V(t)

• 2nd Collision : a crash related occupants to interior parts such as steering wheel and instrument panel.

• 3rd Collision : a crash with inner body such as bone to bone and bone to muscle, etc

Energy Distribution of Inner Car Body

• The fatality rate when not wearing air bags is 9.3 times that when wearing air bags

• In crash events, when wearing the seat belt, the possibility has been reported to be 75% for the following: fatality becoming serious injury; serious injury becoming minor; minor injury becomingwound, whereas the possibility of fatality becoming wound is 49%

Impact Power in the Event of Collision

Comparison of crash velocity and Impact

height APT APT APT APT

Limitation of bearing force in crash events

 When it bears both hands only : about 50Kg

 When it bears both feet only: about 100Kg

 When it bears both hands and feet: about 150Kg

In the event of crash when it bears both hands and feet , the allowable velocity should be less than 7Km/h.

Impact power [Kg] = body weight×deceleration [m/s 2 ]÷gravity

Assumed that a body weight is 70Kg, the impact power goes

70Kg×19.4m/s 2 ÷9.8m/s 2 = 138.6 Kg Therefore, the above resultant proved that the limitation

of bearing force is similar to an impact power.

Correlation between a crash velocity and a free-falling

As a left figure, 40Km/h of crash velocity corresponds to

a free falling of an apartment roof on 6m height, furthermore, this crash velocity equals to an impact power of 30 times compare to a body weight of an occupant.

ActionReaction DirectReaction Indirect

3.2 Types of Seat Belt

1) Point Seat Belt

A seat belt assembly intended to restrain

movement of the chest and shoulder regions

A seat belt assembly intended to restrain movement of the pelvis

2) Component Parts of Belt System

2 Points Belt

3 Points BeltStatic Belt

VSIR (Vehicle Sensitive Inertia Reel)

DSIR (Dual Sensitive Inertia Reel)WSIR (Webbing Sensitive Inertia Reel)

Additional DevicesWebbing ClampTension ReducerConvertible (A/ELR)Pretensioner (Pyro, Mechanical)

Emergency Locking Retractor

TongueAdjust Clip

3) Component Parts of Belt System

Slide Button Type

Sewed to Webbing

Sewed to WebbingSteel Plate StalkBoot Type Stalk (Cable Type Stalk)

SLIP GUIDE (D-RING) Conventional Ring Type + Nylon Coating

Conventional Ring Type + Plastic MoldingPress Stamping Steel + Plastic Molding

Excellent Resin FinishingStrong Tensile Strength WebbingSuperior Resistance to LightLow Hysteresis of Withdrawal / Retraction ForceAnti-Static Electricity

Soft EdgeFashioned Weaving Pattern

SHOULDER HEIGHT

ADJUSTER

Pull TypePush TypeRelease Button Type

3.3 Point Seat Belt Detail

• Point Seat Belt General

Terminology

1) Anchor Plate: component which is assembled in a body of a car The end portion of webbing out of a retractor is fixed onto a body

2) Buckle: a quick release connector which fastens a person in a seat belt assembly

3) Height Adjuster: Because occupants have a different body shape, we need to adjust each body shape to onset point of webbing for being safe and convenience

Therefore, Height Adjuster plays a role to adjusting the position of slip guide upwardly and downwardly.4) Mounting Bracket: means a component which is assembled to the lower portion of retractor

5) Retractor: means an assembly which winds the webbing

6) Slip Guide (D-Ring): means a component which changes the direction of webbing

7) Stay Bracket: means the upper portion of retractor which is fixed onto a body for position fixing of

retractor, assembly convenience, and shaking proof

8) Tongue: a component which is assembled on a buckle

9) Tongue Stopper: means a device which supports the Tongue of webbing for ensuring proper position.10) Warning Switch: means an alarm switch for indicating into an occupant when a seat belt is not engaged.11) Webbing: a band which made a polyester material

12) Web Guide: means a inducing device for working normally during retraction and extraction of the

ANCHOR PLATE BUCKLE

HEIGHT ADJUSTER

WEBBING

TONGUE STOPPER

SLIP GUIDE (D-RING) TONGUE

WEB GUIDE

STAY BRACKET

RETRACTER (TYPE : ELR)

WARNING SWITCH

MOUNTING BRACKET

Static 2 Point Seat Belt (Center)

Terminology

1) Adjustable Tongue: means a component which is assembled on a buckle

2) Anchor Plate: means a component which is assembled in a body of a car The end portion of webbing out of a retractor is fixed onto a body

3) Buckle: means a quick release connector which fastens a person in a seat belt assembly

NLR (Non Locking Retractor) 2 Point Seat Belt (Center)

Terminology

1) Anchor Plate: means a component which is assembled in a body of a car The end portion of webbing out of a retractor is fixed onto a body

2) Buckle: means a quick release connector which fastens a person in a seat belt assembly

Anchor Plate Buckle Adjustable

Tongue

Adjust Clip Anchor Plate

Anchor Plate Buckle (Type : NLR)Retractor Anchor Plate

3) Retractor: means an assembly which winds the webbing.

3.4 ELR (Emergency Locking Retractor)

This Retractor locks only when a vehicle collides or under emergency situation With this, a

passenger moves freely and it can be used conveniently, and recently all Seat belts adopt ELR basically

ELR is classified into three kinds depending on the means of sensing the emergent state of the vehicle However, most vehicles use Dual Sensing Type Retractor

(Vehicle+Web Sensing)

Detects Vehicle Slope and Webbing

Acceleration

1) Basic Operating Principle of ELR

Vehicle Sensing : Detects vehicle’s slope to perform Lock when a vehicle collides or overturning is

occured Sensing Types are Plumb Type and Ball Type, and recently Ball Type superior in sensing capability is used usually

Web Sensing : Sensing the acceleration of webbing, locking is performed, and it uses the difference

of inertia moment occurred by the acceleration transferred to Webbing when colliding

WSIR (Webbing Sensitive Inertia Reel)

Working Principle : In the sudden event of a velocity deviation such as retractor locking

conditions, that is,

① non locking @ less than 0.3g,

② locking @ 0.3g to 2.0g,

③ all locking @ more than 2.0g, a ELR with WSIR behavior has a structure of pulling a webbing according to the inertia force of body

DSIR (Dual Sensitive Inertia Reel)

1) With rotating of lock ring, pawl and ratchet of shaft each other are engaged 2) Then webbing extraction

do not occur.

NON-LOCK LOCK

PAWL FLYWHEEL

MASS FLYWHEEL

HOOK

3.5 WLR (Webbing Clamp Locking Retractor)

• Why Web clamps?

Web clamp retractors, or Web lockers as they are often called, are the most cost effective way of reducing forward movement of occupants in a car accident This is achieved by reducing webbing payout through the elimination of the “film spool” effect also known as cinching

• Can the benefits of web clamps be quantified?

Tests have shown that having a web clamp in the system will reduce payout into the shoulder portion

of the belt by more than 70 mm

This translates into a significant reduction in forward movement of the upper torso and consequently

lower HIC values.

• Why design a webclamp retractor with a load bearing spool?

Customers have for years used traditional retractors with load bearing spools The idea of having a retractor with a plastic spool incapable of taking load seems to them a little revolutionary

This is understandable since they have not been part of the years of development and thousands of hours of testing which finally resulted in the product In practice a load bearing spool is a redundant feature since the whole point of a web clamp is to prevent any load coming onto the spool Once the spool is loaded the webbing on the spool will tighten leading to higher payout By insisting on a load bearing spool customers are in effect building in additional unnecessary cost and weight

3.6 Pretensioner

1) Objectives

• To remove slack from belt

• To reduce forward movement

• To operate right after collision

2) Pretensioner’s Types and Function

Why do we need pretensioner ?

Every person who uses a seat belt has slack in the system The slack may be due to thick clothing, poor seat belt position, after-market tension reducers or hirh friction in the belt system In a crash this slack has to be taken up by occupant forward movement before the seat belt can even start to

restrain the user This results in delayed belt operation, more occupant excursion, higher steering wheel impact velocities and more injury to the user

Types of Pretensioner

(1)Retractor Pretensioner

Retractor pretensioners comprise of an actuator (either spring or pyrotechnic device), a connecting member (bowden cable) and a clutch to connect the actuator to the spool During operation the retractor pretensioner rewinds webbing back onto the spool, this removes the majority of the slack from the diagonal portion of the belt system and a lesser amount from the lap section The amount of webbing pulled into the retractor is reduced slightly by the film spool effect

(2)Buckle Pretensioner

Buckle Pretensioners comprise of an actuator (either spring or pyrotechnic device), a connecting member (bowden cable) and a ratchet device to lock at the bottom of the travel During operation the buckle head is pulled downwards removing slack from both the diagonal and lap portions of the belt system The system has a good mechanical advantage because only 75mm of buckle travel is

required to remove 150mm from the belt system The ratchet mechanism in this area of a belt system has to be capable of withstanding high dynamic loads The buckle on this type of device must be fully

“g” proofed to remain locked during operation

Types of Pretensioner

3) Basic Principle of Pretensioner

The Mechanism to improve the safety of the passengers by removing Spool-out mount, Webbing and passenger slack by reverse rotating of the shaft by the Retractor to which is added a function to decrease the movement of passenger by winding Webbing when collision

E-P/T : Activated by electrical signal due to external detect sensor

M-P/T : Pin Firing activation system by self-sensing detect sensor

B-P/T : Part with adding Pretensioning function to BUCKLE

Crash occurs

Belt rewinding

Belt slack reduction

Electrical signal from external sensor(ECU)

Instant explosive pressure occurs

Passenger injury rate decreases

Gas generator explodes

Pretensioner at the retractor

xx

4) Features of P/T (Ball Type)

Performance of Pretensioner

Maximum bio-mechanical loads on seat belts without causing injuries during pretensioning operation.Retractor pretensioner F pr < 4.7 KN

Lap belt load F l< 4.9 KN

 Operation Condition : When Collision over 15 Km/h

 Rewinding : Below 120mm

 Operational Time : <12ms (below 0.12 seconds)

 Gas Generator Pressure : Max 1000bar

 Operational Force (Static condition) : <2.5KN

SPINDLE

TUBE ASS’Y

REWIND SPRING

GAS GENERATOR

Fc mac = 4,750 N (485 kgf)

Fc mac = 4,750 N (485 kgf)

Fpmac = 4,900 N (500

Fb < 9.5 KN

5) Pretensioner Operating

 Cylinder Type

 Pretensioner Activation

(1)Activation

Under a must-deploy condition, the ECU will supply firing current to the activators when the

microprocessor determines that a deployment is required and activates the firing circuits A safing sensor is not implemented Each time the seat belt pretensioners are activated an internal counter is incremented If this counter reaches the value of 6, the warning lamp is set, and a faults message is written into the non-volatile memory Hereby the ECU unit can be reused 5 times after a seat belt pretensioner activation After 6 times activation, the Control Module should be replaced as new one.(2)Firing circuit

As an option two additional firing circuit for seat belt pretensioners may be provided Each firing circuits can be activated independently The firing circuits are configured so that there is no low-impedance connection from the squibs to either ground or a positive potential inside the ECU in the quiescent state

Initial Explosion 1st Stage Explosion 2nd Stage Stable Stage

Drum Reductio n

Wire Tension Direction SHEAR PIN SHAFT P/T

WIRE

PLATE RELEASE

SHEAR PIN

PLATE DRIVE

Rotation

is prevente

d by Stopper

Wire Winding Direction

T/Bar Distorsion

P/COVER STOPPER

P/RELEASE

The optional seat belt pretensioner circuits are supplied with battery voltage In case of an activation,

an appropriate current flows through the activators via the firing transistors This current depends on the actual battery supply voltage and on the resistance of the external firing loops In all case,

maximum current is limited to approximately 2 -3 A by ECU

6) Pretensioner – Operating Sequence and Principle of Ball type

 Power Unit Assembly

As Propellant is ignited by the electrical signal from the ECU generates high pressure gas, activating the Ball (Gas Generator)

 Operational Function of Pretensioner

Rotation of Retractor Spindle by Aluminum Ball

(1) Gas Generator is ignited by receiving

electrical signal from ECU when collision

(4) As the rotation of Pinion rotates Spindle in

the direction of Return, Webbing is wound

* The quantity of the Ball varies depending on

the specifications of manufacturers

Pipe Piston

Massbodies (AI.-Balls)

Pinion

 Power Unit Assembly

As Propellant is ignited by the electrical signal from the ECU generates high pressure gas,

activating the ball (Gas Generator)

Guide function of Ball movement (Tube)

The place (Ball Trap) where the Ball is stored by the movement after P/T

is activated

Frame where the components of RTR is fabricated and operational function is performed

ScrewTubeAssembled

Tube Cover Assembled

Rivet

Prevents the Ball from moving

in the converse direction that

entered Ball Trap when P/T is

activated (Ball Stop)

Prevents noise generation by inhibiting the movement of the Ball normally

Rotates Pinion by moving along the

tube by the gas pressure

Spring

14 Mass BallsTube

Ball Stop

Gas Generator