DE10296133T5 - safety belt assembly - Google Patents

Abstract

A seatbelt assembly for use in a motor vehicle, said seatbelt assembly comprising a seatbelt connected at one end to a retractor, a sensor for producing a signal indicating the length of the seatbelt retracted from said retractor, a force limiting device associated with said retractor and adapted to provide said seatbelt with a variable force limiting effect, further comprising means for changing the force level applied by the force limiting device and a control unit for receiving a signal from the sensor and for generating at least partially in response to the signal an output signal for controlling the force level changing means.

Description

The present invention relates a safety belt arrangement, and in particular a safety belt arrangement, which is intended for use in a motor vehicle.

A simple safety belt arrangement, how widely in use, includes a pelvic and diagonal seatbelt assembly (or "three-point" seatbelt), one end of the seat belt being at a portion of the vehicle anchored, an intermediate part of the seat belt with a tongue is provided, the detachable to engage with a rigid buckle, and the other End of the seatbelt, which run through a deflection fitting can, is wound on the shaft of a retractor. The Retractor closes a mechanism that blocks the shaft of the retractor, to prevent more Seat belt is released from the retractor when an accident or a potential accident situation is detected. If The seat belt is locked in this way, the seat belt can however under certain circumstances a very big one retarding force to exert on the occupants of the vehicle, causing the occupant very much slowing down quickly, possibly injuring the occupant.

It has therefore been proposed a Provide force limiting device in a safety belt system, wherein the force limiting device is adapted to allow that one certain seatbelt length with a force-limiting or energy-absorbing effect is when very high forces exercised on the safety belt become.

It has been proposed to provide an arrangement in which the force limiting effect can be varied at the beginning or during an accident situation, depending on the load that must be absorbed by the safety belt assembly. An arrangement of this kind is in WO 9749583-A discloses, wherein the shaft of a retractor is provided with a Torsionselementanordnung, which provides the force-limiting effect. The torsion element assembly includes an axially extending torsion bar and a coaxial torsion sleeve. The torsion bar and the torsion sleeve each terminate with a portion having a respective toothed periphery which may be releasably engaged by a pawl member. In this way, the degree of force limiting effect can be selected by selecting either the rod or sleeve or both to provide the force limiting effect.

It is desirable that the force limiting device in a typical accident situation a high force-limiting Effect during the initial stages of an accident provides when the occupant in relation to to the chassis starts to move forward, and a lesser force limiting effect in a subsequent phase of the accident provides when the occupant has moved forward and at one inflating airbag begins to hit. It has therefore been proposed a Provide an arrangement in which the level of force (or energy absorption) the force limiting device is adapted after a predetermined Period following the detection of an accident or a potential accident situation has expired and therefore after the pretensioner has been triggered. An arrangement of this kind, however, has several disadvantages.

Many accidents start with a minor or short interaction with a first object, such as a clash with a relatively low speed car or an impact on the road edge or a guardrail, being on this minor or brief interaction a few moments later a severe collision with a second object follows, such as an oncoming one Vehicle at high speed, a tree or a building. In such a situation would the first interaction can be detected by the sensor in the motor vehicle to detect an accident or a potential accident situation is provided. The sensor could different security devices in the motor vehicle, such as a pretensioner and an airbag, would but also start the operation of the timer, the force limiting device assigned.

In an accident of this kind, the Force limiting device for a period following the slight or short interaction show a high level of strength, the occupant of the vehicle could become but by no means move forward or only a very short one Track during move forward during this period. Before the heavy clash with the second object could the timer has expired, and the force limiting device would therefore only have the lower power level. If then the heavy clash takes place, which causes itself the inmate in proportion Moved forward to the chassis, the force level could be through the force limiting device is provided, far too low be to absorb all the energy of the occupant before the Inmate impinges on the steering wheel or the dashboard.

The present invention seeks after that, to provide an improved seatbelt assembly.

According to this invention, there is provided a seat belt assembly for use in a motor vehicle, the seat belt assembly including a seat belt, one end of which is connected to a retractor, a sensor adapted to generate a signal representing the amount of the seat belt the retractor is issued, a Kraftbegren a device adapted to be associated with the retractor and adapted to allow the seat belt to be deployed with a variable force limiting effect, means for varying the force level exerted by the force limiting device and a control unit for receiving a signal from the sensor and generating, at least partly in response to the signal, an output signal for controlling the means that changes the force level.

Preferably, the retractor includes a pretensioner.

conveniently, the control unit generates the output signal in response to the Seatbelt amount exceeding the seat belt has been pulled out before activation the biasing device has been pulled out.

Alternatively, the control unit generates the output signal in response to the amount of seatbelt over the Seatbelt amount was pulled out immediately after has been pulled out of activating the pretensioner.

In a preferred embodiment are means of locking the seat belt in response to a seized Parameter provided, and the control unit generates the output signal at least partially in response to a predetermined amount of seatbelt, the above a reference length Extracted beyond, wherein means for determining the reference length in or provided shortly after the moment of locking the seat belt are.

In a preferred embodiment is a collision sensor are provided, and the means for determining the reference length suitable, a predetermined period of time after the crash sensor recognized the collision has, pressed to become.

The predetermined period can be 20 to 30 ms and amounts to preferably 20 ms.

Preferably, the control unit suitable, the control signal after a predetermined period, after the predetermined amount of seat belt has been pulled out to produce.

In one embodiment, means for selecting the period provided in response to a signal that the severity of the collision displays.

conveniently, another sensor is provided for generating a signal, the represents a parameter of the occupant and passed to the control unit is, the output signal of the control unit also with the signal from the second sensor.

In one embodiment, the other determines Sensor the weight of the seat occupant.

In another embodiment the other sensor is a capacitive sensor that is suitable determine the water content of the seat occupant.

In a further embodiment the other sensor is an optical sensor that is suitable size parameter of the seat occupant.

Preferably, the control unit suitable to a seat occupant in response to the signal that a Parameter represents being classified into one of several categories, the seatbelt length, the withdrawn must become, about the change to effect in the force limiting effect of the category of User of the seat depends.

conveniently, comprises the variable force-limiting effect several discrete force levels.

Preferably, the force levels comprise two discrete power levels.

Advantageously, a crash sensor provided, which is capable of generating a signal that the severity of the collision represents, and the force-limiting effect is adapted, a Function of the severity of the collision.

Thus, the invention readily is to be understood and more features are to be recognized the invention now by way of example with reference to the accompanying Drawings described.

Show it:

1 a diagrammatic figure illustrating an embodiment of the invention,

2 4 is a graph showing a graph of the force applied to a safety belt as a function of the length of the belt pulled out for a typical person and provided for illustrative purposes;

3 FIG. 3 is a graph showing a graph of the force exerted on a seatbelt and the length of belt pulled out as a function of time for a situation similar to that in FIG 1 corresponds to shown

4 another graphic figure that 2 corresponds, for a heavy person,

5 another graphic figure that 2 . 3 and 4 corresponds, for a light person, and

6 another graphic figure, which relates to a modified embodiment of the invention.

Starting with reference to 1 In the accompanying drawings is a vehicle seat 1 with a seat 2 and a backrest 3 shown. The seat is by a user 4 occupied. The user 4 is shown with applied seat belt, which forms a safety belt assembly according to the invention. The seat belt includes a webbing having one end anchored to a portion of the vehicle seat. In 1 not shown is a tongue which is attached to the seat belt and releasably engaged with a buckle provided on the other side of the seat. Part of the safety belt 5 runs through a deflection fitting 7 and the other end of the seatbelt is with a retractor 8th connected to the Floor is attached. The retractor 8th is adapted to respond to an accident situation and block a shaft in the retractor to prevent further seat belt from being released from the retractor by responding to a sensed parameter such as a predetermined deceleration of the vehicle, and / or blocked in response to the speed of withdrawal of the seat belt from the retractor. The retractor is equipped with a biasing device 9 adapted to rotate in response to the detection of an accident situation, the shaft of the retractor to partially wind the seat belt. Seatbelt assemblies having the features described above are well known and widely used. In this invention, however, alternative mechanisms may be used which block the seat belt in response to a sensed parameter.

In the described embodiment, the retractor includes 8th a variable force limiting device 10 , The force limiting device 10 For example, a continuously variable force limiting device such as an adjustable brake mechanism acting on a pulley or drum that co-rotates with the shaft of the reeling mechanism, or a variable force limiting device providing a plurality of discrete force levels such as a torsional element force limiting device of the type, in the WO 9749583-A is disclosed as described above.

The retractor 8th is with a sensor 11 capable of detecting the amount of seatbelt pulled out of the retractor. Previously, various types of sensors have been proposed that perform this function, and any of these sensors can be used. EP 0 723 895 A discloses an arrangement in which a gear train is provided, which is driven by the shaft of the retractor and causes the rotation of a member having a partially helical outer edge. A sensor includes a spring biased gauge which engages the partially helical outer edge so that when safety belt is pulled out of the retractor, the element with the partially spiraled outer edge rotates and the degree of rotation indicates the length of safety belt being pulled out has been. In another previously proposed arrangement, a member that rotates with the shaft is provided with a plurality of marks arranged at regular intervals, which are detected by an optical sensor. The optical sensor generates a discrete pulse for each mark passing the sensor. Appropriate circuitry coupled to the sensor may determine the length of safety belt that has been deployed by determining the number of rotations or partial rotations of the shaft.

The output signal from the sensor 11 is sent to a central control unit 12 transmitted. The central control unit 12 also receives signals from other sources in the described embodiment. The control unit 12 receives signals from an accident sensor 13 in the training of an acceleration sensor. The acceleration sensor provides an output signal when a deceleration beyond a predetermined threshold is detected. The acceleration sensor may also provide a signal indicative of the severity of the crash. Such an accident sensor 13 is conventional. The control unit 12 may also receive signals from another sensor arrangement, the signals representing a parameter of the user of the seat. In the described embodiment of the invention is a weight sensor 14 provided in the seat 2 incorporated and is capable of generating a signal representing the weight of the user 4 displays. Such a sensor may include piezoelectric sensor devices. In alternative embodiments of the invention, the seat 1 include a plurality of capacitive plates, which are connected to suitable circuitry and are capable of determining the capacitance change between the capacitive plates when the user of the seat sits down on the seat. The capacity change is a function of the seat occupant's total water content, which is closely related to the seat occupant's total weight. Therefore, using an arrangement of this type, it is again possible to generate a signal which is at least approximately related to the weight of the seat occupant.

In addition, in another embodiment of the Invention may be instead of determining the weight of a seat occupant an optional system that optically resembles the seat occupant or the size of at least a part of the seat user. This in turn generates Signal that is at least proportional to the weight of the seat occupant is.

In the presently described embodiment, the control unit is 12 suitable to control not only the biasing and force limiting device, but also an airbag 15 which is arranged in front of the occupant.

While in the described embodiment, the single control unit 12 controlling a number of different elements, the control functions in alternative embodiments could be divided among a number of different, independent control units.

As will be apparent from the following description, in a safety belt assembly according to the invention, a variable force-limiting effect is provided, wherein the variation of the force-generating effect is controlled in response to the seat belt length that has been pulled out de than on the time from the beginning of the accident or the potential accident situation. Additionally, in preferred embodiments of the invention, the seat belt length that must be extended to effect a change in the force limiting effect is determined depending on sensed parameters of the occupant and may also be responsive to a signal from the acceleration sensor indicating the severity of the crash.

With reference to 2 and 3 , which are graphic figures, will now the operation of the safety belt assembly according to 1 in a typical accident for a person with typical or normal weight. The curve of 2 FIG. 12 is a graph of the force-limiting effect force plotted against the seatbelt length withdrawn from the retractor. FIG. The curve of 3 FIG. 12 is a graph of force and pulled strap length versus time, with increasing strap length shown toward the bottom of the page. FIG.

It can be seen that there are two predetermined deceleration forces F ₁ and F ₂ shown in the graph, where the force F _{2 is} greater than the force F ₁ . These forces can be considered, for example, as the forces generated by the torsion bar or torsion tube of an arrangement as in FIG WO 9749583-A are shown shown.

The accident situation starts at point 20 the graphical representation. At this stage, a predetermined length of seat belt was pulled out of the retractor. This is the length of seat belt that is pulled out when the occupant places the seat belt in the position that is in 1 is shown. In this example, this seatbelt length is the seatbelt length commonly used when the occupant, who is of normal or typical size, comfortably sits in an upright position. It is marked L ₀ . If an accident or a potential accident situation due to the accelerometer 13 is detected when the speed change of the vehicle exceeds a predetermined threshold, at time t _0, a signal from the control unit 12 to the pretensioner 9 forwarded to the winding of seat belt on the shaft of the retractor 8th is pressed. The shaft of the retractor therefore rotates, and if desired, the sensor could 11 detect that the seatbelt is being wound up, against a gentle, increasing resistance force which gradually increases to a level F _p until the point where the seatbelt is fully in contact with the occupant is reached. The strap length pulled out of the retractor is now at a minimum L _m . The time is now t _min . The period between t ₀ and t _min is a , as in 3 shown. This period represents the time spent by the pretensioner for biasing the belt. For purposes of explanation, it is assumed that the accident caused by the accelerometer 13 is an initial impact on the roadway edge or guard rail. The slowing down of the chassis of the vehicle is very small, and therefore the occupant does not move forward any appreciable distance relative to the chassis due to the impact on the track edge or guardrail. However, since the accident was detected by the acceleration sensor, the seat belt was biased by the pretensioner, and the occupant was pulled rearward by the pretensioner relative to the chassis.

When the pretensioner device is the Pulling the belt has stopped, leaves the tension on the belt after, and because of the elasticity of the belt and also due to the elasticity of the clothes and the body of the Inmates belt is pulled out. The clothes are now widening of the inmate who initially while compressed the Vorspannphase were, up again. Therefore increased the extended seat belt length, while the clamping force on the Safety belt wears off.

When the belt is pulled out, the locking device responds to the retractor, and the retractor is blocked at time t _lock , as at point 22 in 2 shown. The period from t _min to t _lock has a duration b , as in 3 shown.

At time t _lock , the retractor is blocked by the blocking mechanism associated with the retractor. Typically, t _lock could be 15 to 19 ms after t ₀ . The exact time period between t ₀ and t _lock may depend on factors such as differences in the seat occupant weight or severity of the accident, but mainly on the specific design and operation of the pretensioner.

_Lock could occur just before, at the same time as, or shortly after, the main impact of the accident currently under consideration. During this major impact, the chassis is subjected to a strong deceleration, and possibly also an acceleration in the reverse direction, especially when the impact is a collision with a high speed vehicle moving in the opposite direction.

During this phase of the crash, the belt of the seat belt acts to slow the occupant and possibly accelerate the occupant rearward, depending on the movement of the chassis. During this phase, the force in the belt is increased until the force reaches the higher level F ₂ . When the force reaches the higher level F ₂ , the force limiting device starts to output belt. The speed at which the belt is issued is related to the integral of the relative acceleration (a _rel ) between the chassis and the occupant. The relative acceleration (a _rel ) is the difference between the Be acceleration of the chassis (a _c ) and the acceleration of the occupant (a _o ). Therefore: a rel = a c -a O ,

The acceleration of the chassis is greater than or equal to the acceleration of the occupant. The acceleration of the occupant is related to the force level F ₂ divided by the mass of the occupant. When the mass of the occupant is large, a _o may be small, but a _rel may be large. Therefore, belt is typically issued for a heavier occupant at a higher speed.

The period between t _lock and the point at which the resistance F _{2 is} reached, point 23 As shown in the graph, has a duration c , and this period is usually between 10 and 25 ms. This variation in time is typically due to the weight of the occupant and the exact nature of the crash pulse, that is, the time period between the first impact and the main impact in the accident situation under consideration, and also due to the degree of deceleration or reverse acceleration applied to the chassis of the vehicle is exercised in the particular collision situation.

It is therefore to be understood that the period between t _lock and the point 23 where the force F _{2 is provided} by the force limiting device may have a very different duration depending on the precise circumstances, with a short period of 10 ms occurring in some situations and a period of 100 ms in other situations.

During this phase, between t _lock and point 23 However, the seat occupant moves very little and mainly due to the elasticity of the belt forward.

During this phase, that is during the movement phase with elastic stretching of the belt following the blocking of the shaft and before the seat user has stretched the belt to such an extent that the full resistance force F _{2 of} the force limiting device occurs, the sensor taking the Seatbelt length that has been extended detects a reference measurement at time t _ref and effectively measures or sets a reference safety length that has been pulled out, L _ref . This reference length is used as a starting point in measuring a belt length to be pulled against a specific resistance force F2, as described below.

The point at which the reference measurement is made is as a point 24 in the graphical representation of 2 shown. When making the measurement, t _{ref should be} a selected period, preferably within the period of 20 to 30 ms, more preferably within a period of 20 ms, after t ₀ to ensure that the time t _ref actually in the period c in Connection to t _look , or alternatively, the measurement at time t _{ref can} be made in response to the blocking of the shaft of the retractor.

When the occupant moves forward after the point 23 is reached in the graph, it comes to the resistance F ₂ , when the seat belt is pulled out. This is through the horizontal line 25 shown in the graphic representation. The time taken by the occupant to move forward is immaterial since the resistance force F _{2 is} maintained until a predetermined belt length has been extended, the length being measured after the reference amount L _ref . After a given belt length has been output, as measured by the reference quantity, L _ref to point 26 in the graph and labeled as L _ch , sees the force limiting device 10 no longer the high resistance force F ₂ , but the lower resistance force F ₁ before, as at point 27 shown in the graphic representation. This can be seen as a change from the torsion bar to the torsion tube of the arrangement of WO 9749583-A imagine. There then occurs a continued forward movement of the occupant against the much lower resistance, as in line 28 shown. In a typical case, during this movement phase of the seat occupant, energy is also absorbed by an inflating airbag, as in line 29 shown in dashed lines.

It should be understood that the change in the force level of the force limiting device occurs when a certain amount of seat belt having the measured length L _{ref has been} pulled out, and therefore occurs when a certain amount of energy has been absorbed. In the described arrangement, the seatbelt length that is extended is sized to a datum point, which is in fact the seatbelt length that is pulled out at the moment the retractor is locked. Since the belt length which is pulled out during the period of time c between t _lock and when the force F _{2 is} reached is very short, any reference measurement made in this period is sufficiently accurate. The moment of this "jamming" is somewhat uncertain as to the moment of the initial detection of an accident situation, and the moment when the resistance force F _{2 is} reached is more uncertain and therefore it is appropriate to the moment when the retractor jams is, or a moment that occurs very shortly after that moment in time, as a reference point for determining L _ref to use. Therefore, assuming the distance L _ref is during the period between t _lock and point 23 Therefore, when the resistance force F _{2 is} reached, the measured point L _{ch will be} almost exactly at the desired position, and the amount of energy absorbed before the force change will therefore also be almost exactly the desired amount regardless of the time duration after the beginning of the accident, before the force F _{2 is} reached. The absorbed energy is proportional to the pulled-out belt length multiplied by the force.

The safety belt is pulled out until a maximum extension L _{max is} reached, a point at which the total kinetic energy of the occupant is absorbed. L _max is selected so that the occupant's kinetic energy is absorbed before the occupant actually reaches the steering wheel or windshield.

The transition from the high energy absorption level F ₂ to the low energy absorption F ₁ , as at point 26 and 27 shown in the graph, is performed when a predetermined seat belt length L _{ch has been} pulled out. This predetermined length of seat belt is preferably sized to L _ref as described, but could alternatively be dimensioned after L ₀ , the amount of safety belt pulled out of the retractor just prior to the onset of the accident situation, or L _min the retractor is pulled out just after the pretensioner has biased the seat belt.

It is to be understood that the occupant is restrained during the last portion of the safety belt extraction, not only by the seat belt but also by the air bag, and therefore the speed of withdrawal of the seat belt remains substantially constant, and the total deceleration force, which is applied to the occupant remains essentially constant. 3 shows 30 dashed the situation that would prevail if the airbag did not inflate.

If the seat occupant is heavy or tall, it is preferred that the seat belt length extended against the high resistance force F ₂ should be slightly longer than for a seat occupant of normal weight. 4 is therefore a graphical representation that 2 and in which the same reference numerals have been used, but which refers to a heavy seat user.

How out 4 As can be seen, the starting point of the graph shows a safety _belt length L _0b drawn by the shaft that is less than the length L ₀ as shown in _FIG 2 pulled out. The reason for this is that in a heavy or large seat occupant, the vehicle seat is moved further away from the steering wheel, which means that initially less safety belt has to be pulled out. However, it is equally evident that the distance between L _0b and L _max and also the distance between L _ref and L _{chb are} much larger than the corresponding distances in 2 are. The distance between L _ref and L _chb is larger to allow more energy to be absorbed. However, the distances are still such that the occupant at Lmax has actually not yet reached the steering wheel or the windshield.

With reference to 5 It should be understood that for a light weight occupant, it may be desirable to omit the very strong energy absorption force and apply only the relatively low force. That is why with reference to 5 to note that the initial statement Los greater than the belt pullout L ₀ in 2 is. The reason for this is that in a lightweight seat occupant, the vehicle seat is moved closer to the steering wheel than a normal weight seat user, which means that initially more safety belt has to be pulled out of the retractor to position the seat belt in position.

Following the beginning of the accident at point 20 Seat belt is pulled out from the initial pullout lot to a pullout L _min , as at point 21 shown. During the main crash pulse, that is, during the period c , the seat belt is pulled out of the retractor and the resistance increases until it reaches the force level F ₁ at 23. Subsequently, the occupant can move forward by pulling the safety belt against the resistance force F ₁ , as shown at 25, until the maximum safety belt pullout L _{max is} reached. It will be understood that much less energy is absorbed during the described process because only the relatively low resistance force F _{1 is} utilized. However, this is a sufficient degree of energy absorption for a lightweight occupant because the application of the higher force level F _{2 is} only required for persons of normal or supernormal weight.

6 Figure 10 is a graphic figure relating to an embodiment in which the control unit generates the control signal not only in response to a given seat belt retraction after the locking of the shaft of the retractor, but also in response to the departure of a specific seat belt length and also a subsequent time period. The time period may be set in response to sensed crash conditions such that the time period is related to the severity of the crash, and therefore, the described arrangement may provide an optimal effect. Therefore, in this embodiment, the control unit determines 12 when a predetermined seat belt length (L ₁ ) has been pulled out following t _ref , which is very shortly after the locking of the shaft of the retractor, and starts an internal timer which is a predetermined time period (T ₁ ), so that the control signal Change of the resistance from the higher level F ₂ to the lower level F ₁ causes.

6 For example, for a given severity of an accident, the seat belt length subtracted from the shaft of the retractor according to this embodiment is shown in FIG Time, with the increasing length being shown towards the front of the page, and therefore the figure bears some resemblance to 3 on. The length of safety belt pulled out of the retractor stops at t ₀ at the beginning of the accident 20 in the graphical representation. At a point 21 the seat belt is fully tight against the vehicle occupant, and period a ends and period b begins. During period b , the occupant could easily move forward in the seat, and period b ends at a point 22 in the graph, when the shaft of the retractor locks at t _lock . Shortly after the wave blocked at t _lock , as at point 24 As shown, the seat belt length L _ref pulled out of the retractor is determined or set. During this period following t _lock , the occupant continues to be pushed forward, stretching the belt against a restraining force which increases to level F ₂ during the period c . This period is relatively short for a heavy person, as by line 30 The time period is about 10 ms because the high retention force is quickly reached following the locking of the retractor. The period c for the heavy person by line 30 is marked as ends by line 40 shown, and then the seat belt is pulled out against the deceleration force F ₂ and is marked with C _min . The line 50 shows the desired length L _ch for a heavy person.

Considering the example of a gentle person, as by line 34 indicated that the period c is relatively long and ends only at the point by line 44 is specified. The period is marked C _max . The line 54 shows the desired length L _ch for a light person.

It can be seen that when the time between the point at which a given seat belt length L _{1 has been} pulled out to L _ref until the line representing the desired length L _ch is reached, the time is the same in each case, namely T ₁ . It will also be seen that the same effect can be observed for occupants with decreasing weight, as successively by line 31 . 32 and 33 displayed. The desired length L _ch for each example is by line 60 shown connected.

Therefore, at least in a good approximation, the length L _{ch is} reached after a first predetermined seat belt length L _{1 has been} pulled out and a further belt length has been pulled out during a period T ₁ . As a result, by determining, when the seat belt length L _{1 is} pulled out, and then measuring the time T ₁ for generating the control signal to carry out the change of the resistance force, it is not necessary to make any measurement of any occupant parameter regarding the size of the occupant, thereby increasing the number the sensors are minimized, which must be provided.

The withdrawal speed of the seatbelt is higher in a heavier crash, and therefore the system described automatically adjusts to the severity of the crash. If the system is to function so that it reacts not only in response to the severity of a collision and varies its performance, but also as a function of the weight of the occupant, then the exact values of L ₁ and T _{1 may} depend on the severity of the event Collision can be varied.

While in conjunction with the graphical representations of 3 . 4 and 5 It should be understood that reference has been made to the various operating characteristics provided depending on the weight of the seat occupant, in response to any sensed occupant weight parameter such as a detected seat occupant water content parameter and a sensed parameter the size of the seat user can be provided.

It will be appreciated that in some embodiments, the particular force level exerted by the force limiting device may vary continuously, although in preferred embodiments of the invention, the force level may only change between a limited number of discrete levels. While embodiments are disclosed in which the force level may change between two discrete levels, it will be understood that the force level may alternate between a plurality of discrete levels. It will be appreciated that the force level currently exerted by the force limiting device may be determined as a function of the severity of the accident. Therefore, in a particularly serious accident, an initial level of force can be adjusted to a very high level, which is achieved by the use of both the torsion bar and the torsion tube according to the WO 97/49583-A can be made visible.

To simplify the production can the relationship between the weight or other parameters of the occupant and the Operation of the force limiting device be such that the force limiting device a limited number of discrete modes of operation, such as three Modes as described. Therefore, a seat user is going through estimated the appropriate sensor, to determine which user category is present on the seat is and which operating mode is therefore applicable.

In the example given, therefore, a seat user may be considered "easy", "normal" or "heavy", and the arrangement described then works in the attached Way.

In the present specification, "comprises" means "includes or consists of" and "comprises send "" containing or consisting of ".

Summary

A safety belt assembly for use in a motor vehicle has a safety belt ( 5 ), one end of which is fitted with a retractor ( 8th ), wherein a sensor ( 11 ) generates a signal which is representative of the amount of safety belt pullout from the retractor. A force limiting device ( 10 ) is associated with the retractor to enable a belt webbing with a variable force limiting effect. A control unit ( 12 ) changes this from the force limiting device ( 14 ) applied force level as a function of the length of the webbing extension from the retractor.

Claims (18)

Safety belt arrangement for use in one Motor vehicle, wherein the safety belt assembly with a End belt connected to a retractor, a Sensor for generating a the length of the retracted from the retractor seat belt performing Signal, a force-limiting device associated with the retractor, which is suitable for the safety belt with a variable Force limiting effect is output, further means for changing the force levels exerted by the force limiting device and a Control unit for receiving a signal from the sensor and generating at least in part in response to the signal an output signal for controlling the force level changing Includes. Arrangement according to claim 1, wherein the retractor includes a biasing device. Arrangement according to claim 2, wherein the control unit generates the output signal in response to the seat belt length, the above the extended belt length before activation of the pretensioner was pulled out. Arrangement according to claim 2, wherein the control unit generates the output signal in response to the seat belt length, the above pulled out immediately after activating the pretensioner belt length was pulled out. Arrangement according to claim 2, wherein means for blocking of the seatbelt in response to a detected parameter and the control unit at least partially as the output signal Reaction generated to a predetermined seat belt length, which has a reference length Extracted beyond, wherein means for determining the reference length in or provided shortly after the moment of locking the seat belt are. Arrangement according to claim 5, wherein a collision sensor is provided and the means suitable for determining the reference length are, in a given period of time after the detection of the collision by the collision sensor actuated to become. Arrangement according to claim 6, wherein the predetermined Period is 20 to 30 ms. Arrangement according to claim 7, wherein the predetermined Period is 20 ms. Arrangement according to one of claims 5 to 8, wherein the control unit is suitable, the control signal in a predetermined period after Extracting the specified amount of seat belt to produce. Arrangement according to claim 9, wherein means for selecting the predetermined period and the specified seat belt length as Provided response to a signal indicating the severity of the collision. Arrangement according to one of the preceding claims, wherein a further sensor is provided for generating a signal, the represents a parameter of the occupant and to the control unit is passed, wherein the output signal of the control unit also with is related to the signal from the second sensor. Arrangement according to claim 11, wherein the further sensor determines the weight of the seat occupant. Arrangement according to claim 11, wherein the further sensor a capacitive sensor capable of controlling the water content of the Seat occupant. Arrangement according to claim 11, wherein the further sensor an optical sensor that is suitable, a size parameter of the seat occupant. Arrangement according to one of claims 11 to 14, wherein the control unit is suitable to a seat occupant in response to the signal, the represents a parameter to be classified into one of several categories, with the safety belt length, the withdrawn must become, about the change to effect in the force limiting effect of the category of Seat user depends. Arrangement according to one of the preceding Claims, wherein the variable force-limiting effect comprises a plurality of discrete force levels. Arrangement according to claim 16, wherein the degrees of force include two discrete force levels. Arrangement according to one of the preceding claims, wherein a collision sensor is provided, which is capable of representing the severity of the collision Generate signal and the force limiting effect is adjusted, to be a function of the severity of the collision.