SEAT BELT REELER AND METHOD OF USE THEREOF

Abstract

The invention relates to a reel (8) for a seat belt (30) of a vehicle seat defining a high anchoring point, the seat being equipped with at least one member for detecting the presence of an occupant (1A) and the belt (30) being equipped with at least one pressure sensor, characterized in that the reel (8) is pivotally mounted (F8) reversibly in a plane (P) generally perpendicular to a median axis of the backrest of the seat between an initial position in which the reel (8) is oriented in the direction and is close to the median axis of the backrest and a final position in which the reel is not oriented in the direction of the median axis and is distant from it. The reel (8) is connected to a control module initiating the pivoting (F8) of the reel when at least the pressure measured by the pressure sensor reaches a defined value. The invention also relates to a method of use and a vehicle equipped with such a reel.Figure to be published with the abstract: Fig. 4.

Description

Title of the invention: SEAT BELT WINDER AND ASSOCIATED METHOD OF USE

[0001] The invention relates to a seat belt retractor. The invention also relates to a method of using the retractor. The invention relates to seat belts fitted to the seats of a vehicle. The term vehicle designates a motor vehicle whether the vehicle is a car, a van, a truck, a public transport vehicle, a public works or agricultural machine.

[0002] Each occupant of a vehicle seat is held in position on his seat by a seat belt. The function of a seat belt is, in the event of an accident, to hold the occupant on the seat in order to prevent him from hitting a part of the vehicle or being ejected from the vehicle, while preventing the belt itself from causing injuries or trauma to the occupant. Seat belts are generally of the so-called three-point type: they have a first low anchoring point on one side of the seat base, another anchoring point in the upper part of the seat back and a third removable anchoring point in the lower part of the other side of the seat base relative to the first anchoring point. In general, the anchoring in the upper part is achieved by a reel allowing the length of the belt to be adjusted according to the body size of the occupant of the seat.Thus, a belt passes diagonally across the occupant's torso and transversely across the top of his thighs. Hereinafter, the terms occupant and person will be used interchangeably to designate the occupant of the seat. The belts are sized and positioned in relation to the seat for adults and for people whose morphology, in relation to height and weight, corresponds to that of the majority in the population. However, for people of a smaller build than that commonly encountered, typically for people of approximately 1.50 m to 1.60 m and weighing between 50 kg and 55 kg, impact tests carried out with dummies corresponding to this morphology have shown that during a frontal impact, the state-of-the-art belt fitted to a vehicle seat induces dynamic over-stressing at the neck and upper chest.In other words, in the event of an impact, the belt is not in place at shoulder level but rests against the person's neck and can cause trauma at this level. More specifically, following tests with a so-called 5th percentile impact test dummy, which corresponds to a person of small build, it appears that it is appropriate to move the belt away from the person's neck in order to place it on the shoulder and thus increase the restraint at shoulder level. In the case of tests with a so-called Q10 impact test dummy, which corresponds to the mor . phology of a pre-adolescent, or of a person between 9 and 12 years old, it is appropriate to keep the belt in the initial position, close to the neck. A movement towards the shoulder is not relevant because the shoulder of a pre-adolescent is too low and too sloping to retain the belt. There is therefore a need, in the event of an impact, to modify the initial position of the belt according to the corpulence of the occupant of the seat to obtain optimal restraint of the occupant, whether the latter is a person of small corpulence (5th percentile dummy) or a pre-adolescent (Q10 dummy). KR-A-10-2 496 242 discloses a belt retractor comprising load limiting devices on the belt making it possible to adapt the tension of the belt according to the size of the occupant of the seat in the event of an impact detected by inclination and / or acceleration sensors. A groove in the seat back helps guide and move the belt relative to the occupant's neck.It is therefore necessary to have a suitable seat with a particular backrest. CN-A-114 312 655 discloses a device for detecting the size of the seat occupant and a belt retractor which limits the load on the belt according to the size of the occupant, the position of the belt being identical regardless of the size of the seat occupant. Also known from KR-A-2021 0027 651 or from GB-A-2 425 092 is a belt guide member at the high anchor point on the seatback depending on the weight of the occupant detected by a sensor placed in the seat base. However, these known solutions do not allow for the seat restraint to be optimized as much for a person of average build, small build or a pre-adolescent, without modifying the seat.

[0003] It is to this need that the invention seeks to respond by offering a seat belt reel allowing restraint of the occupant of the seat adapted to the morphology of the occupant and proportional to the tension exerted on the belt.

[0004] To this end, the invention relates to a seat belt reel with three anchor points fitted to a vehicle seat, the reel defining a high anchor point for the seat belt in the vicinity of an upper end of the back of said seat, the latter being fitted with at least one member for detecting the presence of an occupant and the belt being fitted with at least one pressure sensor,characterized in that the reel is pivotally mounted reversibly in a plane generally perpendicular to a median axis of the seat back between an initial position in which the reel is oriented towards and is close to the median axis of the seat back and a final position in which the reel is not oriented towards the median axis and is distant from it and in that the reel is connected to a control module initiating the pivoting of the reel when at least the pressure measured by the pressure sensor fitted to the belt reaches a defined value called a threshold representative of an impact.

[0005] Thus, thanks to the invention, there is a means of optimally restraining the occupant of the seat, limiting the risk of injury, regardless of the build of the occupant of the seat. The invention makes it possible to automatically adapt the position of the belt on the occupant's torso in the event of an impact according to the latter's physical characteristics. Thus, for a small occupant, the automatic pivoting of the reel makes it possible to move the belt away from his neck and head. In this way, the action of the belt on the occupant's torso is effective, the belt being well positioned on the person's shoulder, without risk of injury to the neck and head.

[0006] According to advantageous but not mandatory aspects of the invention, such a seat belt reel may comprise one or more of the following features:

[0007] The winder comprises a so-called stepper motor of the variable reluctance type allowing an electrical pulse to be transformed into an angular movement and coupled to a reduction system.

[0008] The control module is connected to the pressure sensor fitted to the belt as well as at least to the occupant presence detection member fitted to the seat and to a device for fixing a child seat restraint system or a booster seat known as ISOFIX.

[0009] The control module unlocks the rotation shaft of the reel and initiates the pivoting of the reel, according to an angle and a direction of rotation calculated and proportional at least to the value of the pressure measured by the pressure sensor placed on the belt and greater than the defined value called threshold.

[0010] The control module initiates the return of the reel to its initial position, by pivoting, and locks the rotation shaft when the pressure measured by the sensor returns below the defined value called threshold.

[0011] The invention also relates to a method of using a seat belt reel in accordance with any one of the preceding characteristics, characterized in that it comprises at least the following steps: - a) detect the type of seat occupant according to their build using at least the pressure sensor and the presence detection device fitted to the seat, - b) activate or not the unlocking of the rotation shaft of the belt reel according to the type of occupant detected in step a), - c) define at least the value of the rotation angle of the reel when the value of the pressure measured by the pressure sensor fitted to the seat belt is greater than or equal to a defined value called the threshold, - d) return to the initial position of the reel when the pressure value measured by the pressure sensor fitted to the seat belt returns to a value lower than the defined value called threshold, - e) locking the rotation shaft of the reel in the initial position at the end of step d).

[0012] According to advantageous but not obligatory aspects, such a method may comprise one or more of the following steps:

[0013] During steps a) to c), the control module stores the parameters relating to the type of seat occupant, the direction of rotation and the angle of rotation of the reel.

[0014] During step c), at least the rotation angle is proportional to the value of the pressure measured by the pressure sensor equipping the seat belt and to the build of the occupant of the seat.

[0015] The invention also relates to a vehicle equipped with at least one seat belt reel conforming to any one of the preceding characteristics.

[0016] The invention will be better understood and other advantages thereof will appear more clearly on reading the description which follows, given solely by way of non-limiting example and made with reference to the appended drawings in which:

[0017] [Fig-1] is a simplified perspective view of a person occupying a seat of vehicle equipped with a seat belt conforming to a state-of-the-art embodiment,

[0018] [Fig.2] is a view similar and on the same scale as [Fig.l] illustrating the com wearing of the belt of [Fig.l] in the event of an impact,

[0019] [Fig.3] is a partial perspective view on a larger scale of a belt of security in accordance with an embodiment of the invention,

[0020] [Fig.4] is a partial perspective view on a larger scale, illustrating the die placement of the belt of [Fig.3] at the level of the occupant's neck in the event of an impact,

[0021] [Fig.5] is a perspective view similar to [Fig.2] and at the same scale illustrating the operation of the belt which is the subject of the invention according to one embodiment of the invention,

[0022] [Fig.6] is a simplified sectional view, on a different scale, of the stepper motor when the reel is in the initial position,

[0023] [Fig.7] is a view similar to [Fig.6] when the reel is no longer in position initial and

[0024] [Fig.8] is a diagram illustrating the method of operation of the reel according to one embodiment of the invention.

[0025] [Fig.l] is a simplified illustration of a person 1 occupying a seat 2 equipped with a three-point anchorage safety belt 3. Here the safety belt 3 is a belt known from the state of the art. It comprises two anchorage points in the lower part, substantially below the main plane of the seat 4 of the seat 2 and a high anchorage point, substantially at or above the free end on upper end 5 of the backrest 6 of the seat 2. A first fixed anchoring point 7 is, in the example, located at the bottom of the backrest 6. Alternatively, it is located on the structure of the vehicle and not on the seat. A high anchoring point is illustrated by a reel 8, shown schematically and distant from the upper end 5 of the backrest 6 to facilitate readability. The reel 8 is generally fixed either on the structure of the vehicle or on the backrest 6 of the seat 2. A third low anchoring point 9 is said to be removable. It allows the occupant of the seat 2 to fasten and detach the belt 3. The anchoring point 9 is generally located below the plane of the seat 4.When the belt 3 is fastened, it connects the three anchor points 7 to 9 so that a part of the belt passes over the upper thighs of the person 1 occupying the seat 2, close to his waist and another part of the belt 3 is placed diagonally on the torso of the person 1 between one shoulder and the opposite hip. [Fig.l] illustrates a belt of the state of the art restraining a person of so-called 50th percentile build, that is to say a person whose build and height correspond to those of approximately 50% of a given population. Indeed, the approval tests for vehicle safety equipment, therefore seat belts, are carried out with anthropomorphic test devices (AEDs) often referred to as "impact test dummies". These are life-size replicas of human beings, weighted and articulated to simulate the behavior of a human body in the event of an accident.According to the regulations in force, the dimensions and positions of a three-point seat belt are calculated to ensure the optimal restraint of so-called 50th percentile dummies. As illustrated by arrow F in the event of an impact, particularly a frontal impact, person 1 tilts forward, their back tending to move away from the backrest 6 of seat 2 and their head to lean forward. In this case, we note that the position of the belt on the torso of person 1 is approximately in the middle position of the shoulder of person 1, which allows them to be restrained in the event of an impact in an optimal and comfortable manner, without risk of injury. With a person whose build corresponds to that of the dummy used to define the position of the belt, the effectiveness of belt 3 is therefore optimal, as is evident from [Fig.l].

[0026] [Fig. 2] illustrates the use of a belt 3 of the state of the art for a person of small build IA, that is to say of a height of approximately 1.50 m to 1.60 m for a weight between 50 kg and 55 kg, that is to say the build encountered in 5% of a given population, often women, which corresponds to the 5th percentile mannequin. In this case, the belt 3 is positioned very close to the neck and head of the person IA and no longer in a median position on the shoulder. As a result, in the event of an impact, the neck and head of the person IA will be in brutal contact with the belt 3, the latter being able to cause trauma to the neck and / or head. such as friction burns and / or cuts in the event of impact as illustrated in [Fig.2] by reference 10.

[0027] Another case where the person occupying seat 2 does not correspond to the corpulence of a 50th percentile dummy occurs when a child or pre-adolescent occupies seat 2. In this case, a child seat or a booster seat, not shown, is used. Indeed, the regulations in force require that a child under 10 years of age uses a suitable restraint device. This may be a child seat or, when the child weighs more than 15 kg, a booster seat. This equipment is secured to seat 2 by means known per se and subject to international standardization. These means of fixing and securing the child seat or booster seat are known under the name ISOFIX. They include a member for detecting the presence and fixing a child seat or booster seat on seat 2.If in the case of a child under 10 years old the current devices ensure the optimal restraint of the child, the question of the use of the seat belt 3 for a pre-adolescent, i.e. between 10 and 12 years old, arises. The average build of a pre-adolescent aged 10 to 12 is modeled by a so-called Q10 dummy. Impact tests have shown that the belt must generally remain in place near the neck of the pre-adolescent in the event of an impact because his shoulders are too low and sloping to ensure the belt 3 is held in place, even with the use of a booster seat.Thus, we generally encounter four situations in the event of impacts: either the build of person 1 corresponds to the 50th percentile dummy and seat belt 3 as known from the state of the art is effective, or person 1 is a pre-adolescent sitting on a booster seat and in this case, with the ISOFIX device, seat belt 3 known from the state of the art is also effective in the event of an impact, or the person is a pre-adolescent sitting directly on the seat, without a booster seat and then the known seat belt 3 remains relatively effective, or the build of person IA corresponds to the 5th percentile dummy and in this case seat belt 3 from the state of the art is no longer effective.The invention makes it possible to obtain optimal restraint by a three-point safety belt 30, without risk of trauma to the person 1 or IA, regardless of the latter's build, in the presence or absence of a booster seat, the position of the belt 30 being automatically adapted to the person 1 or IA in the event of an impact. It should be noted that although the invention is particularly suitable for rear passenger seats, the invention can nevertheless be used on all the seats of a vehicle.

[0028] As shown in [Fig. 3], in the context of the invention, the safety belt 30 which is the subject of the invention is equipped with a pressure sensor C placed at the level of the upper part of the torso of the person 1 or IA near his shoulder. Such a sensor C is capable of detecting the force exerted by the belt 30 on the person 1, IA, that is to say detecting and measuring the pressure exerted by the belt 30 on the person 1, IA to hold the latter in place on the seat 2, in particular during an impact. It should also be noted that the seat 4 of the seat 2 according to the invention is provided with a member for detecting the presence of a person 1, IA. Such a member, known per se and equipping most vehicle seats 2, makes it possible to detect not only the presence or absence of a person 1, IA on the seat 2 but also their weight, it being understood that a minimum weight is required on the seat 4 for the detection and measurement to take place. Thus, for example, when a person 1, IA is detected but has not fastened their seat belt, a light and / or sound alert signal is triggered in the vehicle. In addition, most seats 2 are also equipped with a system for detecting the presence and attachment of a child seat or booster seat. Such a system, known per se and standardized, is called ISOFIX.It not only detects whether a child seat or booster seat is placed on the seat, but also whether they are properly secured to the seat. It should be noted that with a child seat, the seat belt, generally of the harness type, is incorporated into the seat and adapted to the child's body size. With a booster seat, the vehicle's original 3 or 30 seat belt is used.

[0029] Figures 4 and 5 illustrate the operation of a seat belt 30 equipped with a reel 8, as a high anchor point, according to an embodiment of the invention. As is apparent from [Fig.4], the reel 8 is mounted to pivot reversibly around a theoretical axis A according to the double arrow F8. The axis A is substantially vertical and parallel to a median axis A6 of the backrest 6 when the latter is in the “person 1, IA seated” configuration. For this, the location of the attachment of the reel 8 and its position are adapted to the configuration of the seat 2 of the vehicle. Thus, the invention is suitable, but not exclusively, for seat belts 30 equipping the seats 2 other than those of the driver and the front passenger. These are the so-called second-row seats or the passenger seats in the case of a public transport vehicle.

[0030] When the reel 8 pivots around the axis A, therefore in a plane P generally perpendicular to a median axis A6 of the backrest 6 of the seat 2, this causes the belt 30 to move. Figures 4 and 5 represent the case where the reel 8 pivots reversibly between an initial position, in dotted lines, in which the reel 8 is oriented in the direction of the median axis A6 of the backrest 6 and close to it and a final position where the reel 8 is not oriented in the direction of the median axis A6 and is distant from the axis A6. In other words, the reel 8 can pivot towards the outside of the seat 2 which has the effect of moving the belt 30 away from the neck of the person 1, IA and moving the belt 30 towards the middle of the shoulder of the person 1, IA according to the double arrow F30. The movement of the belt has a limited travel and can be done in one direction or the other, therefore moving away or towards it. of the neck of person 1, IA, this in a manner identical to the movements of the reel 8, while maintaining an optimal position of the belt 30 on the shoulder of person 1, IA.

[0031] The direction of rotation of the reel 8 and the angle of rotation, therefore the travel of the belt 3, are induced and managed by a control module, not illustrated, connected to the sensors mentioned above. It is understood that the movements of the reel 8 and the belt 30 must be carried out simultaneously during an impact, therefore in a short period, of the order of a millisecond.

[0032] The winder 8, in order to be able to pivot under the action of the control module and thus cause the movement along F30 of the belt 30, is preferably but not necessarily equipped with a reluctance stepper motor, therefore with variable magnetic resistance 11, schematically and partially illustrated in Figures 6 and 7. Such a motor 11 comprises a magnetic circuit which variably opposes its penetration by a magnetic field. The motor 11 comprises at least one ferromagnetic bar and a coil. When the coil is powered, knowing that the magnetic field passes as little as possible in the air, the bar aligns with the magnetic field to obtain a minimum reluctance. As the bar has several teeth, there is a rotation of a given angle each time a phase of the motor 11 is powered. The minimum value of the angle is a function of the number of teeth and the angle of rotation depends on the number of phases powered.The motor 11 is here advantageously coupled to a gear reduction system, gears 12 and 15 being illustrated in Figures 6 and 7, in order to increase the torque of the motor 11 while not modifying its size and its power. The motor 11 receives a shaft A materializing the pivot axis of the reel 8. To facilitate reading, the shaft and the geometric axis will be designated by the same reference A. The axis A surrounds a reel 13, the assembly being inserted in the central orifice 14 of the pinion 15 with an air gap 16 between the shaft A and the internal wall of the orifice 14. The air gap 16 receives pads 17, here three in number and made of elastomer. Alternatively, their number and / or constituent material are different. The pads 17 are held integral with the shaft A by ferromagnetic bars 18 also called keys. The keys 18 are inserted into the pads 17, substantially in a central position and are movable in translation in the pads 17.The length of the keys 18 is such that each is also inserted, at least partially, into an orifice of the shaft A. Each key 18 is also movable in translation in each orifice provided in the shaft A.

[0033] In [Fig.6], no current is applied to the coil 13. In this case, the coil 13 is stationary in rotation and the bars 18 are mainly located in the pads 17, while being engaged with the shaft A by one end. In this configuration, the shaft A is stationary in rotation. In this configuration, the pivoting of the reel 8 in one direction or the other is impossible, even in the event of an impact, and the seat belt 30 remains in place on the shoulder of person 1, IA sitting in seat 2. This is the most frequently encountered case.

[0034] In [Fig.7], a current is applied to the coil 13. The latter then attracts the bars or keys 18 towards the center of the coil. The keys 18 move in translation and mainly occupy the orifice made in the shaft A, one of the ends of each key 18 remaining inserted in the pads 17. In this configuration, the keys 18 are in contact by one end with the coil 13. Thus a rotation of the coil will cause a rotation of the shaft A, with the assistance of the pinions 12 and 15. De facto this will cause a displacement of the belt 30 relative to its initial position on the shoulder of the person IA tending to move the belt away from the head and neck of the person IA in the event of an impact.

[0035] The method of implementing the invention, therefore the maintenance or not in the locked position of the shaft A in the event of an impact according to the corpulence of the person 1 or IA is now described with reference to [Fig.8] which illustrates a mode of implementation of the invention. The first step, when a person 1, IA occupies the seat 2, consists of determining his corpulence. For this the control module collects on the one hand the value of the pressures detected and measured by the sensor C and by the presence detection member on the seat 4 and on the other hand the use or not of the ISOFIX system, therefore the use or not of a child seat or a booster seat.If the ISOFIX system is active, therefore if a child seat or a booster seat is used, then, according to a second step, the invention is not implemented, the shaft A remains in the locked position and no pivoting of the reel 8 is possible because the occupant of the seat 2 is a pre-adolescent seated on a booster seat if the belt 30 is used or a child on a child seat when the belt 30 is not used. In these two cases, as indicated previously, there is no need to move the belt 30. If the ISOFIX system is not active, therefore if the occupant of the seat 2 is neither a child nor a pre-adolescent seated on a booster seat, based on the values ​​provided by the sensor C and by the presence detection member, the control module determines whether the person is a person 1, therefore corresponding to the 50th percentile dummy.In this case, the invention is not implemented, the shaft A remains in the locked position and no pivoting of the reel 8 and movement of the belt 30 is possible.

[0036] If the control module detects that the occupant of seat 2 is a person IA whose build corresponds to the 5th percentile dummy, a check is carried out by the control module which checks whether the pressure on the person IA exerted by the belt 30 and measured by the sensor C corresponds or not to that expected for such a person IA when seated on seat 2 and no impact occurs. If this is the case, the invention is then not implemented, the shaft A remains in the locked position. and no pivoting of the reel 8 is possible. If the pressure measured by the sensor C corresponds to a high value for a person IA in the absence of impact, typically a pressure value greater than or at least equal to a previously determined value, then the invention is implemented and an electric current is sent to the coil 13. Such a predetermined pressure value is called a threshold value. Depending on the pressure value measured by the sensor C and other parameters such as, for example, the weight of the person IA measured by the presence detection member, the speed of the vehicle, the initial position of the reel 8 and therefore of the belt 30 relative to the neck of the person IA, the control module defines an activation level and records these parameters to determine the characteristics of the movement of the belt 30, the movement of the belt 30 thus being proportional to the corpulence of the person IA and to the impact.

[0037] The measurement of the pressure exerted by the belt 30 using the sensor C continues and, depending on this value and the activation parameters, the control module defines the direction of rotation of the shaft A, therefore the distance from or approaching the belt 30 to the neck of the person IA as well as the value of the angle of rotation, therefore the distance traveled by the belt 30 away from or towards the neck of the person IA in order to best position the belt on the shoulder of the person IA. All these parameters, measured or determined, are saved by the control module. They will be used during a next activation of the invention to optimize the response, this by learning and / or by the use of artificial intelligence. As a variant, the corpulence parameters of a person 1 or IA regularly occupying the seat 2 can be memorized by the control module in order to optimize the activation of the invention.When the values ​​of the pressure measured by the sensor C fall below the so-called threshold value from which the pressure is considered high and / or when they return to the values ​​known before the impact, the latter is considered to be over. The control module then initiates a pivoting of the shaft A in the opposite direction so that the reel 8 returns to its initial position and deactivates the system by stopping the power supply to the coil 13 which induces the locking of the shaft A, as illustrated in [Fig.6]. Alternatively, the locking only occurs after a time delay.

[0038] It should be kept in mind that the activation or not of the invention, all of the detections and measurements as well as the pivoting or not and the value of the pivoting are determined and carried out in a very short time, of the order of a millisecond, during the impact in order to offer suitable restraint to the person 1 or IA.

Claims

Claims

1. Retractor (8) for a seat belt (30) with three anchor points fitted to a vehicle seat (2), the retractor (8) defining a high anchor point for the seat belt (30) in the vicinity of an upper end (5) of the backrest (6) of said seat (2), the latter being equipped with at least one member for detecting the presence of an occupant (1;IA) and the belt (30) being equipped with at least one pressure sensor (C), characterized in that the reel (8) is pivotally mounted (F8) in a reversible manner in a plane (P) generally perpendicular to a median axis (A6) of the backrest (6) of the seat (2) between an initial position in which the reel (8) is oriented in the direction and is close to the median axis (A6) of the backrest (6) of the seat (2) and a final position in which the reel (8) is not oriented in the direction of the median axis (A6) and is distant from it and in that the reel (8) is connected to a control module initiating the pivoting of the reel (8) when at least the pressure measured by the pressure sensor (C) equipping the belt reaches a defined value called a threshold representative of an impact.;

2. Winder according to claim 1, characterized in that it comprises a stepper motor (11) of the variable reluctance type making it possible to transform an electrical pulse into an angular movement and coupled to a reduction system (12, 15).

3. Retractor according to claim 1, characterized in that the control module is connected to the pressure sensor (C) equipping the belt (30) as well as at least to the member for detecting the presence of an occupant (1; IA) equipping the seat (2) and to a device for fixing a restraint system for a child seat or a booster seat called ISOFIX.

4. Reel according to claim 1, characterized in that the control module unlocks the rotation shaft (A) of the retractor (8) and initiates the pivoting (F8) of the retractor (8), according to an angle and a direction of rotation calculated and proportional at least to the pressure measured by the pressure sensor (C) placed on the belt (30) and greater than the defined value called threshold.

5. Reel according to claim 4, characterized in that the control module initiates the return of the reel (8) to its initial position, by pivoting (F8), and locks the rotation shaft (A) when the pressure measured by the sensor (C) returns below the so-called threshold value.

6. Method for using a seat belt reel according to any one of the preceding claims, characterized in that it comprises at least the following steps: - a) detecting the type of occupant (1; IA) of the seat (2) according to his build using at least the pressure sensor (C) and the presence detection member equipping the seat (2), - b) activating or not the unlocking of the rotation shaft (A) of the reel (8) of the belt (30) according to the type of occupant (1;IA) detected in step a), - c) defining at least the value of the rotation angle of the reel (8) when the value of the pressure measured by the pressure sensor (C) equipping the seat belt (30) is greater than or equal to a defined value called threshold, - d) returning to the initial position of the reel (8) when the value of the pressure measured by the pressure sensor (C) equipping the seat belt (30) returns to a value lower than the defined value called threshold, - e) locking the rotation shaft (A) of the reel (8) in the initial position at the end of step d).;

7. Method according to claim 6, characterized in that during steps a) to c), the control module stores the parameters relating to the type of occupant (1; IA) of the seat (2), to the direction and angle of rotation of the reel (8).

8. Method according to claim 6, characterized in that during step c), at least the angle of rotation is proportional to the value of the pressure measured by the pressure sensor (C) equipping the seat belt (30) and to the corpulence of the occupant (1; IA) of the seat (2).

9. Vehicle equipped with a three-point anchorage seat belt (30) reel (8) fitted to a vehicle seat (2) according to any one of claims 1 to 5.

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