WO1999062747A1

WO1999062747A1 - Method and device for a safety belt

Info

Publication number: WO1999062747A1
Application number: PCT/SE1999/000853
Authority: WO
Inventors: Mats FÄGERHAG; Alf Hedlund; David C. Viano
Original assignee: Saab Automobile AB
Current assignee: Saab Automobile AB
Priority date: 1998-05-20
Filing date: 1999-05-19
Publication date: 1999-12-09
Anticipated expiration: 2000-11-20
Also published as: SE514381C2; SE9801787D0; SE9801787L; DE19983226B4; DE19983226T1

Abstract

In a safety belt (2) in a vehicle, gentle tightening is initiated in the event of the risk of collision in order to bring the belt user into an improved sitting position before any subsequent collision. The gentle tightening is advantageously effected in at least a portion of the safety belt which runs over the shoulder of the belt user. A gentle-tightening arrangement connected to the safety belt (4) advantageously includes a mechanism (20) which is tensioned when the belt is put on and is released in the event of the risk of collision.

Description

_ME_THOD AND DEVICE FOR A SAFETY BELT Technical field

The present invention relates to a method for securely retaining a belt user in a vehicle by means of a safety belt, according to the precharacterizing clause of Patent Claim 1. The invention also relates to an arrangement for such a safety belt, according to the precharacterizing clause of Patent Claim 8.

State of the art

By using safety belts, usually of the three-point type, personal injuries in head-on collisions have been reduced. For the purpose of further reducing the risk of injury, it has become customary to ensure that the safety belt is tightened at the actual moment of impact, so that the belt user is not thrown with unnecessarily great force against a relatively loose- fitting safety belt. This is achieved by a belt tensioner being activated when the retardation of the vehicle has reached a predetermined value, usually roughly 5 g. Such belt tensioners are usually mounted on that side of the person where the shoulder belt and the waist belt meet at the belt buckle and, that being so, provide a tightening primarily of the waist belt, but also of the shoulder belt. In other embodiments, the belt tensioner acts on the upper end of the shoulder belt and, that being so, provides greatest tightening of the shoulder belt, while there is less tightening of the waist belt.

Experience has shown, however, that, in spite of these measures, the contact with the shoulder belt in a collision can nevertheless give rise to chest injuries, especially in older people. The safety belt protects the user against impact with the vehicle, but the user can still be injured by the safety belt itself. For the purpose of reducing this type of injury risk, tests have been carried out using different types of load limitation in the safety belt. One solution, for example, was to use thinner fabric close to the upper fastening point so as to cause the safety belt to yield somewhat at a certain load. For the same purpose, the belt roller is sometimes mounted on an attachment which yields at a certain load. Yet another solution is for the belt roller to be connected to a friction clutch which can be adjusted to varying degrees of load absorption.

It is common to these known solutions that the upper body of the belt user is allowed to move forwards a considerable distance while the safety belt is drawn out. The stress on the belt user is reduced, but it would be desirable to be able to reduce further the stress on and thus the risk of injury to the belt user.

Object of the invention

The object of the invention is to reduce further the risk of injury to a belt user. Another object is to achieve this simply and safely, using simple means.

Description of the invention

By virtue of, according to the invention, initiating a gentle tightening in the event of the risk of collision so as to bring the belt user into an improved sitting position for any subsequent collision, the belt user is made to assume an advantageous position at an even earlier stage.

An arrangement according to the invention is made in such a manner that the safety belt is connected to a gentle-tightening arrangement which is adapted so as to be activated in the event of the risk of collision and then carry out gentle tightening. According to an advantageous variant of the invention, the gentle-tightening arrangement is connected at least to a portion of the safety belt which runs over the shoulder of the belt user.

Further features and advantages emerge from the description and patent claims below.

Description of the figures

The invention is explained in greater detail below with the aid of an exemplary embodiment shown in the appended drawing, in which: Fig. 1 shows a view from the front of a safety belt for a vehicle seat;

Fig. 2 shows a retractor arrangement, belonging to the safety belt in Fig. 1, with the associated tightening arrangement and load-limitation arrangement according to the invention;

Fig. 3 shows an arrangement in which the safety belt is mounted in the vehicle seat;

Fig. 4 shows in greater detail a component in Fig. 2, and Fig. 5 shows a section V-V in Fig. 4.

In a motor vehicle (not shown in greater detail) , there is, according to Fig. 1, a safety belt 2 of the three- point type for a vehicle seat 1. From a retractor arrangement 3 mounted in the vehicle, the belt extends from a first end portion 4 over a shoulder fastening point 5 arranged in the vehicle, which fastening point is usually adjustable for adaptation to the size of the belt user, and forms first a shoulder belt 6 and then a hip belt 7. The free end of the hip belt 7 is fastened at a fastening point 8 in the vehicle. At the transition between the shoulder belt 6 and the hip belt 7, the safety belt can be fixed in the usual manner by means of a belt buckle 9, in which the belt is displaceable, in a holder 10 in the vehicle. The retractor arrangement 3 is of the conventional type which in normal use, against spring force, allows the shoulder belt 6 to be drawn out so as to afford freedom of movement for the user but which, in the event of forceful loading, for example in a collision, prevents the shoulder belt 6 being drawn out.

As can be seen in greater detail in Fig. 2, the retractor arrangement 3 includes a reel 11 with a spindle 12 mounted in a support 13. The spindle 12 is connected via a load-limitation arrangement 14 to a tightening arrangement 15 or belt tensioner which is arranged so as to be activated in the event of a collision in order then to tighten the safety belt and eliminate slack in it. The tightening arrangement 15 can suitably be activated when the retardation of the vehicle has reached a predetermined value, for example 5 g. This can be effected by means of, for example, a sensor 16 connected to the tightening arrangement 15, in which an accelerometer senses the retardation.

In the event of a collision, the sequence of events is as follows:

Within roughly 10 ms, the retardation of the vehicle has reached such a value that the tightening arrangement 15 is activated. As a result, the belt will be tightened, so that slack in the belt is eliminated and so that the belt user is retained securely in the seat. Depending on how fast and powerful the tightening arrangement 15 is, a great tightening force can be generated in the safety belt, with the risk of injury to the user. In order to reduce this risk of injury and limit the maximum permitted and maximum possible tensile force in the safety belt, there is a load- limitation arrangement 14 which makes it possible for the tightening arrangement 15 to slide relative to the reel 11 in the event of strong tightening, or slide if the belt is drawn out with too great a force in the event of a violent collision.

According to Fig. 2, the tightening arrangement 15 can be provided with a gas generator 17 which, when activated, can blow gas out towards a turbine wheel 18 and in this way rotate the reel 11. It is also possible to set the reel 11 in rapid rotation by means of, for example, a pyrotechnic arrangement in which a piston connected to the reel is set in motion in a cylinder.

The load-limitation arrangement 14 can advantageously consist of a friction clutch which can, if appropriate, have an adjustable engagement so as to make it possible to vary the value of the torque transmitted, for example as a function of the size and weight of the user.

In the example shown, the reel 11 has a horizontal spindle, but it is of course also possible to orient the spindle in another manner, for example vertically, and then to use suitable controls in order to obtain the intended movement of the safety belt.

In the embodiment above, the tightening only begins during the collision sequence. According to the invention, however, it is possible to improve the secure retention of the belt user further by already bringing about preparatory tightening of the safety belt in a situation which it is feared could develop into a crash situation, in other words before the collision sequence according to the above has started. This solution requires the driving situation to be analyzed so as to provide a basis for early activation of the tightening. Such a driving situation may be, for example, hard braking or another situation in which the distance to an object in front is decreasing in a dangerous manner. On braking, the retardation can be registered by means of an accelerometer, for example in the sensor 16, and when the value has reached a predetermined safety level, which is lower than the predetermined collision level, the tightening can be started as preparation for a collision sequence. The forewarning time should in this connection be 50-100 ms or more, for which reason the safety level of the retardation should be selected so that an adequately long forewarning is obtained. This forewarning time makes possible relatively slow starting of the tightening arrangement, which is advantageous when an electric motor 19 is used for driving the latter.

In a corresponding way, a distance radar for example, suitably in the sensor 16, can be used to monitor the distance to an object in front and in order to activate the tightening arrangement when the distance has decreased to a critical value or is decreasing at a critical rate. In this case also, a forewarning time of said order is desirable in order to be capable of starting and driving the tightening arrangement electrically. Both these said situations can constitute a stage in a subsequent collision sequence, but it is also possible that the collision may be avoided all the same .

In those cases where a suitable forewarning is obtained, there is usually no need to quick-start the tightening arrangement, for example pyrotechnically, but a continuous electric drive can ensure the desired tightening. The possibility of quick-starting the tightening arrangement should be retained, however, for those situations when forewarning of a collision is for some reason not received.

The maximum permitted tensile force in the safety belt suitably lies within the range 2.0-3.5 k . In this connection, tightening of the belt can be effected at a rate of 5-10 m/s in order to secure the user. The belt tightening may in this respect need to be roughly 140- 250 mm in order to achieve the intended effect, possibly even up to 300-500 mm.

A preparatory tightening of this type results in the belt user being in a better position before a collision and therefore having better chances of coming through the collision without injury. Another possibility is to carry out, even before the preparatory tightening indicated above, a gentle tightening which makes the belt user aware that the sitting position is not the best and should be changed to a more backwardly inclined position. This can be effected by, for example, increasing further the abovementioned forewarning and initially carrying out tightening with a lower force until the normal preparatory tightening state has been achieved, when the tightening force is increased in order to be capable of handling a collision sequence in the manner already indicated. This can be effected by, for example, suitable electric control of an electric motor 19 which drives the tightening arrangement. Another possibility is to arrange for the putting-on of the safety belt to cause a mechanism 20 to be tensioned in the retractor arrangement 3 and for this mechanism, after release via a suitable sensor, for example the sensor 16, to bring about the desired gentle tightening.

In the embodiment according to Fig. 1, tightening takes place only in that portion of the safety belt which runs over the shoulder of the user, but other embodiments are also possible. For example, it is possible to replace the fastening point 8 with a retractor arrangement 3 and then to make the belt buckle 9 fixed on the safety belt. In this way, both the shoulder belt 6 and the hip belt 7 can be tightened by setting the tightening arrangements of both the retractor arrangements in operation. If appropriate, tightening can be effected only at the site of the fastening point 8, with the safety belt running freely at the belt buckle 9.

Instead of anchoring the safety belt 2 in the body of the vehicle as shown in Fig. 1, it is of course also possible to anchor the safety belt in a known manner in the vehicle seat 1 and thus to make the safety belt movable together with the vehicle seat and mount one or more retractor arrangements in the latter. Such an embodiment is shown in Fig. 3.

One possible embodiment of the mechanism 20 is shown in Figs 4 and 5. In a housing 21 mounted on the support 13, there is a bearing 22 in which a spindle 23 is rotatably mounted. This spindle 23 is axially displaceable in the bearing 22 by means of an actuating device 24 and can in this way be brought into or out of rotationally fixed engagement with the spindle 12 of the reel 11. This engagement is in this case achieved by virtue of the spindle ends being designed for positive engagement with one another. Mounted in a rotationally fixed manner on the spindle 23 are a locking member 25, in the form of a toothed locking disc, and one end of a spring member 26, in the form of a torsion spring, the other end of which is fastened in the housing 21. A catch 27, which interacts with the locking member 25, is mounted pivotably in the housing 21 and is acted on by an actuating device 28, by means of which the catch 27 can be brought into and out of engagement with the locking member 25.

The mechanism 20 forms a gentle-tightening arrangement and functions as follows:

When the safety belt 2 is put on, the spindle 23 is in engagement with the spindle 12 and is rotated by the latter when the belt is drawn out. This tensions the spring member 26 which, after the belt has been put on, is kept tensioned by means of the catch 27. The spindle 23 is then brought out of engagement with the spindle 12, after which the safety belt can be used in the conventional manner.

In the event of a collision being feared, indicated by means of the sensor 16 for example, the actuating device 24 brings the spindle 23 into engagement with the spindle 12 and the actuating device 28 brings the catch 27 out of engagement with the locking member 25. The spring member 26 can then rotate the spindle 12 and bring about gentle tightening so as to make the belt user aware that a better sitting position from the point of view of a collision should be sought.

As mentioned, the gentle tightening can be followed by a stronger tightening if the risk of collision persists after gentle tightening. The mechanism 20 is tensioned only in connection with the belt being put on and can thus be used only for gentle tightening. The magnitude of the spring force and suitably selected gears determine the force required in order to tension the mechanism and the force that can be generated by the mechanism.

In addition to the embodiments shown here relating to three-point belts, other embodiments are of course possible within the scope of the invention. The idea of the invention can therefore also be used in the case of, for example, two-point and four-point belts.

In an alternative embodiment, a retractor arrangement 3 can be positioned at the holder 10 and act on the latter so that the belt-tightening according to the invention can be brought about. In this case, the holder 10 is designed with a retractable section (not shown) . In the event of such tightening, the other end portions of the belt are fixed. It is understood of course that the details of the constructional design of the retractor arrangement can be varied within the scope of the invention. The rotating belt-tightening movement can, if appropriate, be replaced by a linear belt-tightening movement.

Claims

Patent Claims

1. Method for securely retaining a belt user in a vehicle by means of a safety belt (2), characterized in that a gentle tightening is initiated in the event of the risk of collision so as to bring the belt user into an improved sitting position for any subsequent collision.

2. Method according to Claim 1, characterized in that gentle tightening is effected in at least a portion of the safety belt which runs over the shoulder of the belt user, so that the belt user receives a stimulus to assume a more backwardly inclined sitting position.

3. Method according to Claim 1 or 2, characterized in that the possibility of gentle tightening is activated when the belt is put on, and in that gentle tightening is initiated when the risk of collision is judged to exist.

4. Method according to any one of Claims 1-3, characterized in that energy for gentle tightening is stored when the belt is put on.

5. Method according to any one of Claims 1-3, characterized in that energy for gentle tightening is taken from the electrical system of the vehicle.

6. Method according to any one of Claims 1-5, characterized in that the risk of collision is assessed continuously while the vehicle is travelling, and in that gentle tightening is activated at a predetermined first level of risk of a collision.

7. Method according to Claim 6, characterized in that gentle tightening is followed by a stronger tightening at a second, higher level of risk of a collision.

8. Arrangement for a safety belt (2) in a vehicle, characterized in that the safety belt is connected to a gentle-tightening arrangement which is adapted so as to be activated in the event of the risk of collision and then carry out gentle tightening.

9. Arrangement according to Claim 8, characterized in that the gentle-tightening arrangement (15) is connected at least to a portion of the safety belt which runs over the shoulder of the belt user.

10. Arrangement according to Claim 8 or 9, characterized in that the gentle-tightening arrangement (15) includes an operating member (26) which is adapted to store energy which is generated when the safety belt is drawn out and put on.

11. Arrangement according to Claim 10, characterized in that the operating member (26) is a spring member.

12. ^ΓÇó Arrangement according to Claim 11, characterized in that the spring member (26) is a torsion spring.

13. Arrangement according to Claim 8 or 9, characterized in that the gentle-tightening arrangement includes an electric motor which is connected to the electric system of the vehicle.