Pretensioner and a safety belt arrangement having the same

Abstract

A tensioner (100) comprising: a base element (110) attached to a vehicle, a torsion shaft (120) having a first side and a second side rotatably mounted on the base element (110), a traction wire (140), and a pulling device (150) configured to pull on the traction wire (140) to rotate the torsion shaft (120), wherein the tensioner (100) comprises a torsion tube (130), wherein a belt (20) configured to restrain an occupant is wound around an outer surface of the torsion tube (130), the torsion tube (130) itself being twisted, causing a section of the belt (20) to be pulled out when the belt (20) is pulled while the torsion shaft (120) is fixed, characterized in thatthat the torsion tube (130) has a first end section attached to an outer surface of the torsion shaft (120) and a second end section rotatably mounted on the outer surface of the torsion shaft (120); the traction wire (140) is wound around a second end section of the torsion shaft (120) on a side opposite the point where the torsion tube (130) is attached to the torsion shaft (120) in a direction opposite to a winding direction of the belt (20); the first end section of the torsion tube (130) is attached to the outer surface of the torsion shaft (120) by means of a fastening element (131) and the second end section of the torsion tube (130) is rotatably mounted on the outer surface of the torsion shaft (120) by a bearing (132); that if the vehicle is involved in a low-speed collision, the towing device (150) is not activated will be the second end section of the torsional wave (120),around which the traction wire (140) is wound, is fixed and a first end section of the torsion shaft (120) is set into a rotational state, wherein the torsion shaft (120) is twisted when the torsion tube (130) is rotated by the tension on the belt (20), which allows a section of the belt (20) to be unwound. When the vehicle is involved in a high-speed collision, the torsion shaft (120) and the torsion tube (130) are rotated in the winding direction of the belt (20) by the activation of the traction device (150), thereby tightening the belt (20) and holding the passenger firmly in the seat (10). When the vehicle is involved in a high-speed collision and when the tension on the belt (20) increases beyond a limit load, the torsion shaft (120) is prevented from unwinding in the unwinding direction of the belt. (20) to be filmed,wherein the torsion tube (130) is twisted and a section of the belt (20) is unwound.

Description

Background of the inventionField of the invention

[0001] The present invention relates to a pretensioner and a seat belt assembly comprising the same, which is capable of adjusting a belt tension differently depending on the conditions of a collision of a vehicle and protecting the body of an occupant by keeping the belt tension below a limit load. Description of related technology

[0002] A safety belt assembly (also referred to as a seat belt assembly) is a device designed to securely hold an occupant in his or her seat and is designed to protect the occupant during a collision or accident that may occur while driving.

[0003] The seat belt assembly includes: a belt known as a webbing, a retractor mounted on the vehicle body for winding (such as winding) or unwinding one end of the belt, a fixing anchor (or attachment anchor) for fixing (or attaching) the other end of the belt to the vehicle body, and a tongue plate attached to a buckle located on the opposite side of the fixing anchor while being movably mounted in the center of the belt.

[0004] The seatbelt assembly may also include a pretensioner configured to tighten any slack in the belt by exerting tension on the belt by immediately pulling on the belt at the onset of a collision. The pretensioner may be of a type in which the pretensioner is integrally formed with the retractor, or of a type in which the pretensioner is disposed on the side of the attachment anchor or an anchor of the buckle to pull on the belt or buckle.

[0005] However, a seat belt assembly that uses a pretensioner can cause harm to the passenger if the tension on the belt (or belt tension) increases too much at the onset of an accident due to the pretensioner mechanism.

[0006] The information disclosed in this Background of the Invention section is provided merely to facilitate a better understanding of the general background of the invention and should not be construed as an acknowledgment or any form of indication that this information constitutes prior art already known to those skilled in the art. Brief overview

[0007] Numerous aspects of the present invention are directed to providing a pretensioner configured as a load limiter to maintain tension below a limit load and a seat belt assembly including the pretensioner.

[0008] Numerous aspects of the present invention are also directed to providing a pretensioner and a vehicle having the same, which is configured to adjust the tension on a belt (or belt tension) differently depending on the conditions of a collision of the vehicle.

[0009] According to one aspect of the present invention, a pretensioner (or belt pretensioner) comprises: a base member which is fixed to a vehicle, a torsion shaft, both sides of which are rotatably supported on the base member, a torsion tube which has one end portion (e.g. axial end portion) fixed to an outer surface of the torsion shaft and the other end portion (e.g. axial end portion) rotatably supported on the outer surface of the torsion shaft, wherein a belt (or seat belt) which is adapted to restrain an occupant is wound around the outer surface of the torsion tube, a traction wire (or pulling wire or pulling cable) which is wound around an end portion of the torsion shaft on one side corresponding to the location orside opposite to which the torsion tube is attached to the torsion shaft, is wound in a direction opposite to a winding direction of the belt, and a pulling device configured to pull the traction wire therein to rotate the torsion shaft.

[0010] The traction device may include: a cylinder fixed to the base member, a piston disposed within the cylinder and connected to an end portion of the traction wire, a gas generator configured to move the piston in a direction for pulling the traction wire by supplying gas into an interior of the cylinder, and a one-way locking device disposed in the piston to prevent the piston from moving in its reverse direction.

[0011] The pretensioner may further include a rotation limiting device disposed at an end portion of the torsion shaft on the side opposite to the position or side where the traction wire is wound and configured to prevent the torsion shaft from being rotated in a direction of unwinding of the belt after the gas generator is activated.

[0012] The rotation limiting device may include: a ratchet wheel fixed to an end portion of the torsion shaft, a pawl configured to engage and lock the ratchet wheel by a forward and backward movement and to prevent the ratchet wheel from being rotated in the unwinding direction of the belt at a time when the ratchet wheel is locked, a housing configured to accommodate a portion of the pawl configured to move in a forward and backward direction, and a gas supply pipe configured to connect the housing and the cylinder and supply gas into the housing to activate the pawl while the gas generator is activated.

[0013] The pretensioner may further comprise: a control unit configured to control (e.g., regulate) an operation of the gas generator by detecting a collision of a vehicle, wherein the control unit may be configured to determine whether the collision is a low-speed collision or a high-speed collision based on set information, and to activate the pulling device when it is determined that a high-speed collision occurs.

[0014] The one-way locking device may comprise: one or more inclined grooves formed on an outer surface of the piston facing an inner surface of the cylinder and having a depth that decreases in a direction in which the piston is moved by activation of the gas generator, and locking elements received in the one or more grooves.

[0015] A torsional stress of the torsion shaft can be set such that it is lower than that of the torsion tube.

[0016] According to another aspect of the present invention, a pretensioner (or belt pretensioner) comprises: a base member fixed to a vehicle, a torsion shaft having both sides rotatably supported on the base member, a belt (or seat belt) wound on an outer surface of the torsion shaft to restrain a passenger, a traction wire wound around an end portion of the torsion shaft in a direction opposite to a winding direction of the belt, and a pulling device configured to pull the pulling wire (traction wire) therein to rotate the torsion shaft.

[0017] According to another aspect of the present invention, a seat belt assembly includes a belt (or seat belt) configured to restrain a passenger, and a pretensioner (or belt pretensioner) configured to apply tension by pulling on an end portion of the belt, the pretensioner comprising: a base member fixed to a vehicle, a torsion shaft having both sides rotatably supported on the base member, a torsion tube having one end portion (e.g., axial end portion) fixed to an outer surface of the torsion shaft and another end portion (e.g., axial end portion) rotatably supported on the outer surface of the torsion shaft, the belt being wound around the outer surface of the torsion tube, a traction wire wound around an end portion (e.g., axial end portion) of the torsion shaft on a side corresponding to the location orside opposite to which the torsion tube is attached to the torsion shaft, is wound in a direction opposite to a winding direction of the belt, and a pulling device configured to pull the traction wire therein, thereby rotating the torsion shaft.

[0018] The methods and apparatus of the present invention have other features and advantages which will be apparent and more particularly set forth in the accompanying drawings incorporated herein and the following detailed description, which together are arranged to explain certain principles of the present invention. Character list Fig. 1 shows a safety belt assembly with a pretensioner according to an exemplary embodiment of the present invention, Fig. 2 is a structure of a pretensioner according to an exemplary embodiment of the present invention, Fig. 3 is a side view of the pretensioner when viewed from a direction of an arrow III of Fig. 2, Fig. 4 is a cross-sectional view of the pretensioner taken along a line IV-IV of Fig. 2, Fig. 5 is a block diagram for controlling an operation of a pretensioner according to an exemplary embodiment of the present invention, Fig. 6 shows a mechanism of a pretensioner in a low-speed collision according to an exemplary embodiment of the present invention and Fig. 7 and Fig. 8 show a mechanism of a pretensioner in a high-speed collision according to an exemplary embodiment of the present invention.

[0019] It should be understood that the accompanying drawings are not necessarily to scale, but rather present a somewhat simplified representation of numerous features illustrating the basic principles of the invention. The specific embodiments of the present invention disclosed herein, including, for example, specific dimensions, orientations, positions, and shapes, will be determined in part by the precise intended application and use environment.

[0020] In the figures, like reference numerals refer to the same or equivalent parts of the present invention. Detailed description

[0021] Reference will now be made in detail to numerous embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to these exemplary embodiments. On the contrary, the invention(s) is / are intended to cover not only the exemplary embodiments, but also numerous alternatives, modifications, equivalents, and other embodiments which may be encompassed within the spirit and scope of the invention as defined in the appended claims.

[0022] Fig. 1 shows a seat belt assembly with a pretensioner according to an exemplary embodiment of the present invention. Referring to Fig. 1, the safety belt arrangement may comprise: a belt (or safety belt) 20 to secure a seat 10 to hold the seated passenger firmly, a retractor attached to the vehicle 30 for winding (winding up) or unwinding an end section of the belt 20 , a pretensioner 100 for attaching the other end section of the strap 20 and to exert tension by pulling on the strap 20 at the moment of an accident and a tongue plate 60 which is mounted on an opposite side of the pretensioner 100 arranged buckle 50 is attached, while in the middle of the belt 20 is clamped or is movably attached to the belt 20 along the belt.

[0023] The seat belt arrangement may cause tension in the belt 20 by immediately pulling on the belt 20around the passenger's belly by operating the pre-tensioner 100 at the beginning of a collision. Accordingly, the seat belt arrangement may prevent the belt 20 is loosened at the beginning of a collision, which keeps the passenger permanently firmly in the seat 10 is held.

[0024] Although Fig. 1 the pretensioner 100 at a specified end section of the belt 20 arranged, it is also possible that the pretensioner 100 a fastening element 51 the buckle 50 on the opposite side. In this case, the pretensioner 100 Sagging in the belt 20 by exerting tension on the belt 20 in such a way that the buckle 50 is applied in the event of a collision.

[0025] The pre-tensioner 100cannot only be designed to adjust the tension by pulling on the belt 20 at the beginning of an accident, but can also be set up as a load limiter to reduce the tension of the belt 20 below a limit load when the tension of the belt 20 increases rapidly, thereby protecting the body of a passenger. The pretensioner 100 can also adjust the tension on the belt 20 depending on the collision conditions of a vehicle. The structure and operation of the pretensioner 100 will now be described in detail.

[0026] Fig. 2 is a diagram illustrating the structure of a pretensioner according to an exemplary embodiment of the present invention. Fig. 3 is a side view of the pretensioner when viewed from the direction of an arrow III of Fig. 2 and Fig. 4 is a cross-sectional view of the pretensioner taken along a line IV-IV of Fig. 2.

[0027] Referring to Fig. 2 to Fig. 4 the pretensioner 100 comprise: a base element attached to the vehicle 110 , a torsion wave 120 , which is rotatable on the base element 110 is carried, a on the outside of the torsion shaft 120 arranged torsion tube 130 , around whose outer surface the belt 20 is wound, a traction wire (or a pulling wire or a pulling rope) 140, which is wound around an end portion of the torsion shaft 120 wound or windable, a pulling device 150 which is used to pull on the traction wire 140 for rotating the torsion shaft 120 and a rotation limiting device 170 which is attached to an end section (e.g. an axial end section) of the torsion shaft 120is arranged on a side opposite the point or side where the traction wire 140 is wrapped.

[0028] The basic element 110 can be made of steel and attached to the vehicle body, e.g. by fastening bolts. The base element 110 has shaft supports 111 and 112 on both sides to connect both end sections of the torsion shaft 120 to be worn rotatably.

[0029] The torsion wave 120 is formed to be longer than the distance between the two shaft supports 111 and 112 of the base element 110 to be, and is rotatable on shaft support balls 111a and 112a the shaft carrier 111 and 112 supported so that both end sections of the torsion shaft 120 outwards from the shaft supports 111 and 112 protrude.

[0030] The torsion tube 130is formed to be shorter than the distance between the two shaft supports 111 and 112 of the base element 110 to be, and is outside the torsion wave 120 between the two shaft supports 111 and 112 arranged. The belt 20 is, as in Fig. 4, several times around the outer surface of the torsion tube 130 wound and one end section of the belt 20 is attached to the torsion tube 130.

[0031] As in Fig. 2, an end section of the torsion tube 130 on the outer surface of the torsion shaft 120 by means of a fastening element 131 and the other end section is rotatable on the outer surface of the torsion shaft 120 through a warehouse 132 worn. The fastening element 131 can be attached to one end section of the torsion tube 130 and the outer surface of the torsion shaft 120by welding. Accordingly, the torsion tube can 130 , if the belt 20 is pulled while the torsion shaft 120 is fixed, which results in a certain section of the belt 20 is pulled out.

[0032] The traction wire 140 is around an end section of the torsion shaft 120 on the opposite side to a fixed position of the torsion tube 130 , i.e. to the fastening element 131 , in a direction corresponding to a winding direction of the belt 20 wound in the opposite direction. A coil body 141 for winding the traction wire 140 can be attached to an end section of the torsion shaft 120 One end section of the traction wire 140 is on the coil body 141 and wrapped several times around it and the other end section is connected to the pulling device150 Accordingly, the torsion tube 130 if the towing device 150 on the traction wire 140 pulls, together with the torsion shaft 120 can be turned and it can be attached to the belt 20 be pulled while it is wrapped around the outer surface of the torque tube 130 is wrapped.

[0033] The pulling device 150 may comprise: a base element 110 attached cylinder 151 , a piston 152 , which is arranged and adapted to move forwards and backwards in the cylinder 151 to move, and with one end section of the traction wire 140 connected to a gas generator 153 for supplying gas into the cylinder 151 to the piston 152 in the direction of pulling the traction wire 140 to move, and one in the piston 152 arranged one-way locking device 154to limit or prevent the backward movement of the piston 152 .

[0034] The cylinder 151 can have a bending section 155 on the side where the traction wire 140 enters, and the gas generator 153 can be at an end section of the bending section 155 be arranged to direct gas towards the piston 152 into the cylinder 151 The traction wire 140 enters the inside of the bend section 155 and is connected to the piston 152 connected, while it is supported by a curved wire carrier 156 Accordingly, the gas generator can 153 supplied gas the piston 152 which in turn is attached to the traction wire 140 can pull, which the torsion wave 120 caused to rotate. Reference number 157 in Fig. 2 denotes a plurality of in the bending section 155 formed gas passages.

[0035] Although the cylinder 151 in the present embodiment, the bending section 155 the shape or arrangement direction of the cylinder 151 not limited to this. The cylinder 151 may have the shape of a straight line and may be parallel to the direction in which the traction wire 140 Although not shown, a roller can be arranged on one side of the cylinder 151 be arranged to guide the traction wire 140 to pull gently.

[0036] The one-way locking device 154 may have: one or more inclined grooves 154a which is on the inner surface of the cylinder 151 facing outer surface of the piston 152and have a depth gradient which is in the direction in which the piston 152 is moved when the traction wire 140 is pulled, decreases, and locking elements shaped like a ball or a roller 154b which are arranged in the one or more inclined grooves 154a.

[0037] The one-way locking device 154 allows the piston 152 , against or in the cylinder 151 to move, since, as in Fig. 7, the locking elements 154b in a relatively wide section in the inclined grooves 154a are arranged when the piston 152 in one direction to pull on the traction wire 140 is moved.

[0038] However, the locking elements 154b , as in Fig. 8 shown when the piston 152is to be moved or is moved in the reverse direction, to the relatively narrow section in the inclined grooves 154a moves and between the piston 152 and an inner wall of the cylinder 151 clamped, causing the piston 152 in the cylinder 151 This means that the one-way locking device 154 a backward movement of the piston 152 limited, restricted or even prevented.

[0039] Referring to Fig. 2 is the piston 152 in the initial state on the side of the bending section 155 near the gas generator 153 and a movement in the direction of the bending section 155 is by an engagement with an engagement projection 158 inside the cylinder 151 In addition, the torsion wave 120prevented from rotating in a direction of unwinding of the belt 20, since the belt 20 is wound around the torsion shaft 120 wound traction wire 140 with the piston 152 while maintaining a certain tension in the initial state. Accordingly, in the initial state, the end portion of the torsion wave 120 , by which the traction wire 140 is wound.

[0040] In the initial state, the other end portion of the torsion shaft 120 on the opposite side of the traction wire 140 rotatable. Accordingly, the torsion shaft 120 , if the torque tube 130 by the tension of the belt 20, which, as in Fig. 6, a specific section of the belt 20 allowed to be unwound. For the present mechanism, the torsional stress of the torsion shaft 120be adjusted so that it is lower than that of the torsion tube 130 is.

[0041] Referring to Fig. 2 and Fig. 3 the rotation limiting device 170 have: a ratchet wheel 171 , which is attached to the end section of the torsion shaft 120 on the side opposite to the point at which the traction wire 140 is wound, a locking pawl 172 which is designed to move forward and backward with the ratchet wheel 171 to engage and lock it, and the rotation of the locking wheel 171 in the unwinding direction of the belt 20 locks, a housing 173 , which is a closed compartment 173a for receiving a section of the pawl 172 to be able to move forward and backward, and a gas supply pipe 174 which connects the housing 173and the cylinder 151 connects.

[0042] The ratchet wheel 171 is prevented from rotating clockwise (in the direction of unwinding of the belt 20 ) despite the tension of the belt 20 to turn when the pawl 172 , as in Fig. 3, moved upwards and engaged with a tooth 171a which occurs at the edge section of the ratchet wheel 171 In contrast, the ratchet wheel, as in Fig. 7, together with the torsion shaft 120 rotated while the torsion shaft 120 in the winding direction of the belt 20 is turned when the traction wire 140 by operating the gas generator 150 is pulled. The ratchet wheel 171 can the torque tube 130 wound belt, which is pulled accordingly. In other words, the ratchet wheel can 171in the winding direction of the belt 20 be turned, even while the pawl is 172 in the state in which the pawl 172 due to the pressure of the gas supplied into the housing 173 through the gas supply pipe 174 supplied gas moves upwards.

[0043] Fig. 5 is a block diagram for controlling (e.g., regulating) the operation of a pretensioner according to an exemplary embodiment of the present invention. Referring to Fig. 5 can be a control unit 180 based on information from a collision sensor 181 and a vehicle speed sensor 182 , which are arranged in the vehicle, detect whether the vehicle has collided or is involved in a collision. The control unit 180can determine whether the vehicle's collision is a low-speed collision or a high-speed collision by comparing the actual (current) vehicle speed with predetermined vehicle speed information. If it is determined that the vehicle is involved in a high-speed collision, the control unit fires 180 the gas generator 153 to the pulling device 150 If it is determined that the vehicle is involved in a low-speed collision, the control unit operates 180 the pulling device 150 not.

[0044] Next, the operation of a pretensioner according to an exemplary embodiment of the present invention in connection with Fig. 6 to Fig. 8 are described. Fig. 6 shows a mechanism of a pretensioner in a low-speed collision according to an exemplary embodiment of the present invention and Fig. 7 and Fig. 8 show a mechanism of a pretensioner in a high-speed collision according to an exemplary embodiment of the present invention.

[0045] If the vehicle is involved in a low-speed collision, the towing device 150 , as in Fig. 6, is not activated. In this case, an end section of the torsion shaft remains 120 , by which the traction wire 140 wound, and the other end portion is set in a rotating state. Accordingly, the torsion shaft 120 be twisted when the torsion tube 130 due to the tension on the belt 20 is rotated, which corresponds to a specific section of the belt 20allowed to be unwound. This case can reduce the force exerted on the passenger's torso, thereby preventing damage to the passenger's torso.

[0046] When the vehicle is involved in a high-speed collision, the gas generator ignites 153 under the instructions of the control unit 180 , whereby the pulling device 150 , as in Fig. 7. In this case, the piston 152 in the cylinder 151 moved by the pressure of the gas, causing the traction wire 140 pulled and the torsion shaft 120 in the winding direction of the belt 20 is rotated, while the torsion shaft 120 wound traction wire 140 is processed.

[0047] Since the torsion tube 130 is also rotated as soon as the torsion shaft 120 is activated by the traction device150 is turned, the belt 20 on the outer surface of the torsion tube 130 wound, whereby the belt tension or the tension on the belt 20 at the beginning of a collision. In the present case, in which the towing device 150 activated, the gas inside the cylinder 151 is forced into the housing 173 the rotation limiting device 170 through the gas supply pipe 174 fed, whereby the pawl 172 is caused to move the ratchet wheel 171 to lock the locking wheel 171 from being rotated in one direction. The rotation limiting device 170 In particular, the torsion shaft 120 allows only in the winding direction of the belt 20 to be rotated while preventing rotation in the opposite direction.

[0048] In the event of a high-speed collision, the torsion shaft 120 and the torsion tube 130 in the winding direction of the belt 20 by activating the pulling device 150 rotated, whereby, as in Fig. 7 shown, the belt 20 tightened and the passenger firmly in the seat 10 is held.

[0049] Meanwhile, in the case of a high-speed collision, when the tension on the belt 20 increases beyond a limit load, the torsion shaft 120 is prevented from moving in the unwinding direction of the belt 20 by the traction wire 140 at one end portion and the rotation limiting device 170 at the other end section, as in Fig. 8. This case may result in the torque tube 130 is twisted and a certain section of the belt 20In other words, the torsion tube can 130 if the tension of the belt 20 more than the torsional stress of the torsion tube 130 increases, twisted and the belt 20 allow to be unwound to create a belt 20 to keep the applied load below the limit load, thereby protecting the passenger.

[0050] As described above, the pretensioner 100 According to embodiments of the present invention, the tension of the belt 20 at a force equal to the torsional stress of the torsion shaft 120 in a low-speed collision and can reduce the tension of the belt 20 at a force equal to the torsional stress of the torsion tube 130 in a high-speed collision. In other words, the tension of the belt 20higher in the high-speed collision than in the low-speed collision, since the torsional stress of the torque tube 130 larger than that of the torsion wave 120 is.

[0051] While the present embodiment proposes that the rotation limiting device 170 the torsion wave 120 from being rotated in such a direction that the torsional stress of the torque tube 130 than the tension of the belt 20 in a high-speed collision in the above-mentioned embodiment, it is possible to use the rotation limiting device 170 in other embodiments. In this respect, the tension of the belt 20 at the torsional stress of the torsion shaft 120 in both high-speed and low-speed collisions.

[0052] According to various embodiments of the present invention, a pretensioner may be configured as a load limiter for maintaining the tension of a belt below a limit load; when the tension of the belt increases due to a collision, a torsion shaft (or a torsion tube) is twisted and the belt is pulled out in a pay-out direction.

[0053] Furthermore, according to various embodiments of the present invention, the pretensioner can be operated such that the torsional stress of the torsion shaft acts as the tension of the belt since a traction gear is not activated in a low-speed collision, and the torsional stress of the torque tube, which has a relatively large torsional stress, acts as the tension of the belt since the traction device is activated in a high-speed collision. That is, the tension on the belt can be adjusted differently depending on the vehicle collision conditions.

[0054] For ease of explanation and for accurate definition in the appended claims, the terms "upper", "lower", "inner", "outer", "top", "bottom", "up", "down", "front", "back", "rear", "inside", "outside", "inward", "outward", "inside", "outside", "forward" and "backward" are used to describe features of the exemplary embodiments by reference to the positions of such features as illustrated in the figures.

[0055] The foregoing description of specific exemplary embodiments of the present invention is provided for purposes of illustration and description only. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed, since numerous modifications and variations are obviously possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and use various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the appended claims and their equivalents.

Claims

[1] Pretensioner (100), comprising: a base element (110) which is attached to a vehicle, a torsion shaft (120) having a first side and a second side, which are rotatably supported on the base element (110), a torsion tube (130) having a first end portion fixed to an outer surface of the torsion shaft (120) and a second end portion rotatably supported on the outer surface of the torsion shaft (120), wherein a belt (20) adapted to restrain an occupant is wrapped around an outer surface of the torsion tube (130), a traction wire (140) wound around an end portion of the torsion shaft (120) on a side opposite to the position at which the torsion tube (130) is attached to the torsion shaft (120) in a direction opposite to a winding direction of the belt (20), and a pulling device (150) configured to pull the traction wire (140) to rotate the torsion shaft (120). [2] Pretensioner (100) according to claim 1, wherein the pulling device (150) comprises: a cylinder (151) attached to the base element (110), a piston (152) arranged in the cylinder (151) and connected to an end portion of the traction wire (140), a gas generator (153) adapted to move the piston (152) in a direction for pulling the traction wire (140) by supplying gas into an interior of the cylinder (151), and a one-way locking device (154) arranged in the piston (152), to prevent the piston (152) from moving in its reverse direction. [3] The pretensioner (100) according to claim 2, further comprising: a rotation limiting device (170) arranged at the end portion of the torsion shaft (120) on the side opposite to the position where the traction wire (140) is wound and configured to prevent the torsion shaft (120) from being rotated in a direction of unwinding of the belt (20) after the gas generator (153) is activated. [4] Pretensioner (100) according to claim 3, wherein the rotation limiting device (170) comprises: a ratchet wheel (171) attached to an end portion of the torsion shaft (120), a pawl (172) adapted to engage with the ratchet wheel (171) through a forward and backward direction thereof and to lock it and to prevent the locking wheel (171) from being rotated in the unwinding direction of the belt (20) at a time when the locking wheel (171) is locked, a housing (173) adapted to receive a portion of the pawl (172) so as to be adapted to move in a forward and backward direction thereof, and a gas supply pipe (174) which is arranged to connect the housing (173) and to connect the cylinder (151) to supply gas into the housing (173) to activate the pawl (172) while the gas generator (153) is activated. [5] Pretensioner according to one of claims 1 to 4, further comprising: a control unit (180) configured to control operation of the gas generator (153) by detecting a collision of the vehicle, wherein the control unit (180) is configured to determine whether the collision is a low-speed collision or a high-speed collision based on set information, and is configured to activate the traction device (150) if it is determined that the collision is a high-speed collision. [6] Pretensioner according to one of claims 2 to 5, wherein the one-way locking device (154) comprises: at least one inclined groove (154a) formed on an outer surface of the piston (152) facing an inner surface of the cylinder (151) and having a depth that decreases in a direction in which the piston (152) is adapted to be moved by activation of the gas generator (153), and Locking elements (154b) received in the at least one inclined groove (154a). [7] Pretensioner (100) according to one of claims 1 to 6, wherein a torsional stress of the torsion shaft (120) is set to be lower than that of the torsion tube (130). [8] Pretensioner (100), comprising: a base element (110) which is attached to a vehicle, a torsion shaft (120) having a first side and a second side rotatably supported on the base member (110), wherein a belt (20) is wound on an outer surface of the torsion shaft (120) to restrain a passenger, a traction wire (140) wound around an end portion of the torsion shaft (120) in a direction opposite to a winding direction of the belt (20), and a pulling device (150) configured to pull the traction wire (140) to rotate the torsion shaft (120). [9] Pretensioner (100) according to claim 8, further comprising: a control unit (180) which is configured to control an operation of the towing device (150) by detecting a collision of the vehicle, wherein the control unit (180) is configured to determine whether the collision is a low-speed collision or a high-speed collision based on set information, and is configured to activate the traction device (150) if it is determined that the collision is a high-speed collision. [10] A safety belt assembly comprising a belt (20) adapted to restrain a passenger and a pretensioner (100) adapted to exert tension by pulling on an end portion of the belt (20), the pretensioner (100) comprising: a base element (110) which is attached to a vehicle, a torsion shaft (120) having a first side and a second side, which are rotatably supported on the base element (110), a torsion tube (130) having a first end portion fixed to an outer surface of the torsion shaft (120) and a second end portion rotatably supported on the outer surface of the torsion shaft (120), wherein the belt (20) is wrapped around an outer surface of the torsion tube (130), a traction wire (140) wound around an end portion of the torsion shaft (120) on a side opposite to the position at which the torsion tube (130) is attached to the torsion shaft (120) in a direction opposite to a winding direction of the belt (20), and a pulling device (150) configured to pull the traction wire (140) to rotate the torsion shaft (120).

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