Retractor pretensioner assembly

Abstract

The seat belt pretensioner system includes a pretensioner tube that is in fluid communication with a gas generator, and a pretensioner rod, the pretensioner rod having a proximal end portion disposed toward the gas generator and a distal end portion disposed toward the outlet of the pretensioner tube. In the pre-actual state, the pretensioner rod is disposed inside the pretensioner tube, and in the post-actual state, it is adapted to move within the pretensioner tube toward the pretensioner wheel when the gas generator is activated. The pretensioner rod includes a projection formed radially on the rod to connect with the pretensioner tube and restrict the rod from moving out of the pretensioner tube in the pre-actual state. The pretensioner rod is configured to avoid rod delamination and reduce energy consumption when the polymer rod deforms during pretensioning.

Description

[Technical Field]

[0001] This disclosure relates to a seat belt restraint device for restraining a vehicle occupant, and more specifically, to a device for applying pretension to a seat belt. [Background technology]

[0002] The information contained in this section is provided solely to give background information relating to this disclosure and does not constitute prior art.

[0003] Seat belt restraint systems, which secure occupants within vehicle seats, play a crucial role in mitigating occupant injuries in vehicle collision situations. Conventional so-called "three-point" seat belt restraint systems generally consist of a lap belt section extending across the occupant's pelvis and a shoulder belt section crossing the upper body, which are fastened together or formed by a continuous length of seat belt webbing. The lap belt section and shoulder belt section are connected to the vehicle structure by fasteners.

[0004] Typically, a belt retractor is provided to retract the belt webbing and may further act to manage the belt tensile load in a collision situation. A seat belt restraint system that is manually deployed by the occupant (a so-called "active" type) also typically includes a buckle attached to the vehicle body structure by a fastener. A latch plate attached to the belt webbing is received by the buckle, allowing the belt system to be fastened to enable restraint and released to enable boarding and alighting from the vehicle. When deployed, the seat belt system effectively restrains the occupant during a collision or rollover event.

[0005] OEM vehicle manufacturers often provide seat belt restraint systems that have a pretensioning device (also known as a "pre-pretensioner") that applies tension to the seat belt either during or before the vehicle impact to improve occupant restraint performance. The pretensioner removes slack in the webbing, allowing the belt restraint system to engage with the occupant early in the collision sequence. One type of pretensioner acts on the webbing retractor to apply tension to the belt.

[0006] Various designs of retractor pretensioners exist today, including a type known as a roto-pretensioner, which incorporates a gas generator to generate working gas using gunpowder. Generally, ignition of gunpowder or other flammable material generates gas pressure in a chamber containing a piston for imparting motion to a driving element such as a piston or rod element, which is disposed within the pretensioner tube. The pretensioner tube engages with a retractor spool pretensioner wheel, winding the retractor spool pretensioner wheel and pulling in the webbing.

[0007] One of the drive elements, such as the pretensioner rod, is made of a polymer material. Generally, polymer materials have a higher coefficient of linear thermal expansion, and as a result, a polymer rod disposed inside a pretensioner tube made of metal material will have a much larger dimensional change than the metal tube when the operating environment temperature fluctuates, such as from high daytime temperatures to low nighttime temperatures, or between summer and winter. In this case (i.e., during repeated temperature cycles), the polymer rod may move or "creep" in the direction of lower frictional resistance, and as a result, the polymer rod may move out of the pretensioner tube before applying pretension, potentially interfering with one of the components in the pretensioner system, such as the spool drive pinion. This phenomenon can interfere with the free movement of the webbing spool during the normal operation of the retractor.

[0008] A further problem with polymer rod type pretensioners is that, under certain operating conditions, the polymer rod may not properly engage with the pretensioner wheel (drive pinion) during pretensioning, resulting in insufficient pretensioning force being transmitted to the seat belt pretensioning retractor assembly. Since the pretensioner wheel is made of a material with higher hardness than the polymer material of the rod, delamination or breakage of the rod may occur during pretensioning, reducing the effective transfer of energy to the retractor spool. [Overview of the project]

[0009] This disclosure relates to a seat belt pretension retractor assembly, including a spindle and a frame, for use in a vehicle. In particular, this disclosure relates to a seat belt pretensioner system for a seat belt pretension retractor assembly, including a pretensioner rod, a housing, a guide plate, and a pretensioner tube. In this disclosure, the pretensioner rod is in the form of a flexible, elongated rod formed from a polymer material. Furthermore, the pretensioner rod is designed to include a creep prevention function to avoid the aforementioned design and performance limitations, namely, delamination or breakage of the rod during pretension, and also to avoid interference of the rod with the pretensioner wheel caused by thermal cycling environments or aging in the pre-operation state of the rod.

[0010] According to one aspect of the present disclosure, a seat belt pretensioner system for use in a seat belt pretensioner retractor assembly includes a pretensioner tube in fluid communication with a gas generator, and a pretensioner rod having a proximal end portion disposed toward the gas generator and a distal end portion disposed toward the outlet of the pretensioner tube. The pretensioner rod is disposed within the pretensioner tube in a pre-actual state and is adapted to move within the pretensioner tube toward a pretensioner wheel in a post-actual state when the gas generator is activated. Furthermore, the pretensioner rod includes a projection formed radially on the rod to be coupled with the pretensioner tube to restrict the rod from moving out of the pretensioner tube in a pre-actual state.

[0011] According to a further aspect of the present disclosure, the pretensioner tube includes a tube stopper formed radially inward in the exit region of the tube to engage with a projection formed on the distal end portion of the pretensioner rod. In the pre-actual state, the interaction between the projection and the tube stopper restricts the movement of the pretensioner rod toward the pretensioner wheel when thermal creep occurs in the rod.

[0012] According to a further aspect of the present disclosure, the projection of the pretensioner rod is designed to be sheared or scraped by the pretensioning force and rod movement generated by the gas generator, thereby allowing the pretensioner rod to move freely out of the pretensioner tube in the post-actual state. The projection of the pretensioner rod is coupled to a tube stopper located in the outlet region of the pretensioner tube, thereby causing the distal end of the rod to be substantially aligned with the second tube end of the pretensioner tube in the pre-actual state.

[0013] In a further aspect of this disclosure, the projection of the pretensioner rod protrudes radially from the concave portion of the pretensioner rod. Furthermore, the pretensioner rod is in the form of a flexible, elongated rod formed from a polymer material.

[0014] According to another aspect of the present disclosure, a seat belt pretensioner system for use in a seat belt pretension retractor assembly having a housing and a spindle includes a pretensioner tube in fluid communication with a gas generator, a pretensioner rod having a proximal end portion disposed toward the gas generator, a distal end portion disposed toward the outlet of the pretensioner tube within the pretensioner tube, and a chamfer formed on the distal end portion of the pretensioner rod, and a pretensioner wheel rotatably mounted to the housing and fixedly coupled to the spindle. The pretensioner wheel includes an annular body portion and a plurality of vanes having a first side wall and a second side wall formed around the circumference of the body portion. Furthermore, in a cross-section of the pretensioner wheel perpendicular to the axis of rotation of the pretensioner wheel, the pretensioner wheel has a root circle defined by connecting each of the root sections of the vanes and a tip circle defined by connecting each of the tip points of the vanes. A first point is defined on the surface of the first side wall when the circular line defined between the tip circle and the root circle intersects the first side wall, and a second point is defined on the surface of the second side wall when the circular line intersects the second side wall, thereby defining the vane distance between the first point and the second point in the pocket formed between the two adjacent vanes. The chamfered portion of the rod has a chamfered length that is greater than the vane distance of the pretensioner wheel.

[0015] According to a further aspect of the present disclosure, in a side cross-sectional view of a rod along its longitudinal axis, the chamfered portion is tapered, having a starting point on the distal end of the rod, above the centerline of the rod along its longitudinal axis, and an ending point on the circumferential edge of the rod, thereby defining the length of the chamfer as the distance from the starting point to the ending point.

[0016] According to a further aspect of the present invention, the chamfer portion of the rod is formed to have a flat shape or a curved shape. Further, the circular line is defined as an intermediate circle located between the tip circle and the base circle.

[0017] According to a further aspect of the present disclosure, the pretensioner rod is configured to avoid peeling of the rod and reduce energy consumption when the rod is engaged with the vane during pretensioning.

[0018] According to a further aspect of the present disclosure, in a side sectional view of the rod along the longitudinal axis, a first radial thickness defined in the non-concave section of the rod is greater than a second radial thickness defined in the concave section of the rod. Further, the length of the non-concave section along the longitudinal axis of the rod is greater than the tip distance between two adjacent vane tips of the pretensioner wheel. The deformation depth of the pretensioner rod is 15% to 50% of the radial thickness of the rod when the pretensioner rod is engaged with the vane of the pretensioner wheel during pretensioning.

[0019] Further details and advantages will become apparent from the following detailed description of the accompanying drawings. The drawings are provided herein for illustrative purposes only and are not intended to limit the scope of the present disclosure.

Brief Description of the Drawings

[0020] The drawings shown herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. [Figure 1] A perspective view of the occupant restraint system is shown. [Figure 2] A perspective view of the occupant restraint system with various components removed to show the seat belt retractor assembly including the pretensioner system of FIG. 1. [Figure 3] A plan view of a seat belt retractor assembly including a pretensioner system according to an exemplary form of the present disclosure. [Figure 4] Figure 3 is an exploded view of the seat belt retractor assembly, including the pretensioner system. [Figure 4A] This is a cross-sectional view of a pretensioner tube having a pretensioner rod, a seal, and a piston. [Figure 5] This is a side view of the pretension rod and stopper according to the present disclosure. [Figure 5A] Figure 5A is a side view of the pretensioner rod and stopper according to this disclosure, and Figure 5A is a top view of the pretensioner rod and stopper of Figure 5. [Figure 5B] Figure 5B is a side view of the pretensioner rod and stopper according to this disclosure, and Figure 5B is a bottom view of the pretensioner rod and stopper of Figure 5. [Figure 5C] Figure 5C is a side view of the pretensioner rod and stopper according to this disclosure, and Figure 5C is a cross-sectional view of the pretensioner rod along the line 5C-5C in Figure 5. [Figure 5D] Figure 5D is a side view of the pretensioner rod and stopper according to this disclosure, and Figure 5D is a cross-sectional view of the pretensioner rod along the line 5D-5D in Figure 5. [Figure 5E] Figure 5E is a side view of the pretensioner rod and stopper according to this disclosure, and Figure 5E is a cross-sectional view of the pretensioner rod along the line 5E-5E in Figure 5. [Figure 6] This is a perspective view of a pretensioner wheel having multiple hollow vanes according to the present disclosure. [Figure 7A] Figure 7A is a partial plan view of a pretensioner wheel having a pretensioner rod positioned in the outlet region of the pretensioner tube in a conventional pretensioner system. [Figure 7B] Figure 7B is a cross-sectional view of a pretensioner wheel according to this disclosure, in a pre-operation state, in which the pretensioner rod is positioned in the outlet region of the pretensioner tube. [Figure 8] This is a cutaway view of the pretensioner wheel along line 8-8 in Figure 6. [Figure 8A]Figure 6 is a cutaway view of the pretensioner wheel along line 8-8. Figure 8A is a detailed view of the pretensioner wheel in Figure 8. [Figure 8B] Figure 6 is a cutaway view of the pretensioner wheel along line 8-8. Figure 8B is a cross-sectional view of the pretensioner wheel according to this disclosure, with the pretensioner rod in the actuated state. [Figure 9A] Figure 9A is a detailed side view of the pretensioner rod shown in Figure 5. [Figure 9B] Figure 9B is a side cutaway view of the pretensioner rod and pretensioner wheel when the pretensioner rod is engaged with some of the vanes of the pretensioner wheel during pretensioning.

[0021] Throughout the drawings, please understand that corresponding reference numbers indicate similar or corresponding parts and features. [Modes for carrying out the invention]

[0022] The following descriptions are purely illustrative and are not intended to limit the disclosure or any use or application thereof. Throughout the drawings, corresponding reference numerals indicate similar or corresponding parts and features.

[0023] Figure 1 shows a vehicle seat 10 and seat belt assembly 12 for a vehicle according to an exemplary embodiment of the present disclosure. The seat belt assembly 12 generally includes a seat belt webbing 14 having a shoulder belt portion 16 extending from an upper guide loop or fastener 18 to a latch plate 20, and a lap belt portion 22 extending from the latch plate 20 to a lower fastener 24. The latch plate 20 may include a loop portion 26, through which the webbing 14 extends. The latch plate 20 is inserted into a seat belt buckle 28 to lock and unlock the seat belt assembly 12. The seat belt buckle cable or strap 30 fastens the seat belt buckle 28 to a part of the vehicle structure, either directly or in cooperation with other components. It will be understood that variations of the latch plate 20 and the seat belt buckle 28, as well as other methods of attaching the seat belt webbing 14 to the vehicle, including their attachment to the webbing 14 and associated vehicle structure, may also be used.

[0024] The seat belt webbing 14 is located within the vehicle seat 10 (in an integrated structural seat design) or can be extended from a retractor assembly 32 (shown in Figures 2 and 3) structurally coupled to the vehicle body, so that the effective length of the seat belt webbing 14 is adjustable. When the buckle latch plate 20 is fastened to the seat belt buckle 28, the seat belt assembly 12 defines a three-point restraint between the fastener 18, the buckle latch plate 20, and the lower fastener 24. Any other preferred configurations, such as alternative positions for the retractor assembly 32, the buckle latch plate 20, and the lower fastener 24, may be used in conjunction with this disclosure.

[0025] Referring to Figure 2, an isometric view of the seat belt assembly 12 of the described embodiment is shown separated from the vehicle and shows the retractor assembly 32. The retractor assembly 32 includes a spool assembly 34 and a gas generator 36 mounted on a frame 38. The spool assembly 34 is connected to and houses the seat belt webbing 14 of the shoulder belt portion 16, while the ends of the lap belt portion 22 of the webbing 14 are fixedly engaged with a fixing point, such as the frame 38, or another part of the vehicle such as the seat 10 or floor pan.

[0026] Referring to Figure 3, the spool assembly 34 includes a spindle 40 that engages with the shoulder belt portion 16 of the seat belt webbing 14 and rotates to wind up or unwind the seat belt webbing 14. A torsion “clock” or “motor” type spring is carried within a spring end cap 42 and biases the spindle 40 in the rotational direction to retract the seat belt webbing 14. The spool assembly 34 may further incorporate other spool control mechanisms known according to the prior art, including pretensioners, inertia and webbing-sensing locking devices, torsion bar load limiters, or other belt control devices. The spool control systems referred to herein may include any system that controls the rotational movement of the webbing spool and thus controls the unwinding and retracting of the seat belt webbing. One such spool control system is a motor-assisted retractor. The spool lock device typically incorporates a vehicle-sensing locking mechanism having an inertial sensing element such as a rotating ball or pendulum, which engages a pretensioner wheel of the spool control system to prevent further extension of the seat belt webbing 14 from the spindle 40. The webbing-sensing locking device is configured to sense rapid extension of the seat belt webbing 14 and lock the retractor assembly 32. Various electronic sensing mechanisms for detecting the extension of the seat belt webbing 14 and / or the connection of the latch plate 20 to the seat belt buckle 28 may also be incorporated into the retractor assembly 32.

[0027] During normal vehicle operation, the retractor assembly 32 allows the seat belt webbing 14 to extend to give the occupant a certain amount of freedom of motion. However, if an impact or a situation that could cause an impact is detected, the retractor assembly 32 locks to prevent extension and secures the occupant to the seat 10. For example, when the vehicle decelerates to a predetermined speed, the retractor assembly 32 is locked. Due to the free extension of the seat belt webbing 14, the seat belt assembly 12 often develops slack during normal use.

[0028] Figure 4 is an exploded view of a retractor assembly 32 including a pretensioner system 44, according to an exemplary embodiment of the present invention. Referring to Figures 3 and 4, the retractor assembly 32 is operably connected to a spool assembly 34 and further incorporates a pretensioner system 44 operable to rotate a spindle 40 to apply pretension. As is known to those skilled in the art, the retractor pretensioner tightens the seat belt webbing more firmly against the occupant in the initial stages of a detected vehicle impact. This is provided to reduce the forward motion or displacement of the occupant in response to the deceleration force of a vehicle impact or rollover.

[0029] As shown in Figures 3 and 4, the pretensioner system 44 includes a pretensioner tube 52 that communicates with a gas generator 36 at a first tube end 51 of the pretensioner tube 52. The gas generator 36 is used to provide expansion gas in response to an ignition signal. As is known in the art, for example, a vehicle includes a sensor array that transmits signals indicating emergency events such as collision events, crashes, or rollovers. The vehicle sensors may be specific impact sensors or conventional vehicle sensors (e.g., longitudinal or lateral acceleration sensors, or otherwise part of a control system having a set of multiple sensors). Any other impact sensors known to those skilled in the art may also be readily used in conjunction with the seat belt assembly 12 of this disclosure. An electronic control unit, such as a central processing unit (CPU) or other controller, receives the signals and controls the seat belt assembly 12 to respond by tightening the vehicle's seat belt webbing 14 (e.g., via the activation of the pretensioner).

[0030] In Figure 4, the pretensioner tube 52 has a pretensioner rod 200 disposed inside it, for example, a polymer rod or a plastically deformable polymer rod (also shown in Figure 5), the pretensioner rod 200 has an elongated shape and is flexible within the tube 52. More specifically, as will be discussed in more detail below, the polymer rod 200 has a generally straight shape when disposed outside the pretensioner tube 52 before insertion into the pretensioner tube 52, and when inserted into the tube 52, it bends and flexes according to the meandering shape of the tube 52, as shown in the exploded view of Figure 4.

[0031] As shown in Figures 3 and 4, the retractor assembly 32 includes a spool assembly 34 mounted on a frame 38. More specifically, the spool assembly 34 rotates relative to the frame 38 and winds up the seat belt webbing 14 attached to the spool assembly 34. The frame 38 includes a housing 54 having components of a pretensioner system 44, and has a guide plate 58 inside the housing 54. As shown in Figure 4, the spool assembly 34 includes a pretensioner wheel 56 disposed within the housing 54. The pretensioner wheel 56 is mounted on a spindle 40. The rotation of the pretensioner wheel 56 rotates the mounted spindle 40 and winds up the seat belt webbing 14 attached to the spindle 40.

[0032] Furthermore, Figure 4A shows a pretensioner tube 52 having a polymer rod 200, which is inserted into the tube 52 together with a piston 72 and a stopper 55 attached to the polymer rod 200. In the embodiment of the exemplary embodiment, the pretensioner rod 200 has a substantially circular cross-section. According to other exemplary embodiments, the rod 200 may have a non-circular cross-section, such as a rectangular cross-section, a triangular cross-section, or other polygonal cross-section that allows the rod 200 to be inserted into the pretensioner tube 52 and conform to the meandering shape of the tube 52 when inserted, as shown in Figure 4A. The polygonal cross-section may rotate along the length of the rod 200 to create a helical shape. In addition, in Figure 4A, the pretensioner tube includes a tube stopper 50 formed near a second tube end 53 (i.e., the exit region of the tube 52) to connect with the polymer rod 200 which is first inserted into the tube 52.

[0033] Figures 5, 5A, and 5B show that the pretensioner rod 200, when positioned outside the pretensioner tube 52 (before being inserted into the tube 52), has a generally linear shape and extends longitudinally L from a proximal end portion 202 to a distal end portion 204. The proximal end portion 202 is positioned toward the gas generator 36 when the pretensioner rod 200 is installed within the pretensioner system 44. According to an exemplary embodiment, the pretensioner rod 200 has a cross-section that varies along its length, defining a non-concave portion 206 and a concave portion 208 that defines a recess (first recess) 210. As shown in Figure 5, the concave portion 208 extends along most of the total length of the pretensioner rod 200 from the proximal end portion 202 to the distal end portion 204. In one embodiment, the concave portion 208 extends to the most distal end 205 of the distal end portion 204 of the pretensioner rod 200. In addition, the proximal end portion 202 includes a non-concave portion 206, and the recess 210 terminates at the most distal position of the non-concave portion 206. Furthermore, as shown in Figure 5B, the pretensioner rod 200 includes a projection 224 that radially protrudes from the first recess 210 of the distal end portion 204 so as to engage with the tube stopper 50 of the pretensioner tube 52 when the pretensioner rod 200 is first inserted into the tube 52 (i.e., before pretension is applied).

[0034] The pretensioner rod 200 also includes a knob 212 extending proximal to the proximal end portion 202. The stopper 55 has a negative feature portion 214 formed thereon, which receives the knob 212 and connects the stopper 55 to the proximal end portion 202 of the pretensioner rod 200. According to one embodiment of the present disclosure, the negative feature portion 214 and the knob 212 are sized such that the stopper 55 is compression-fitted, for example, interlocked onto the knob 212, thereby permanently connecting the stopper 55 to the pretensioner rod 200. Other forms of connection and / or fixation of the stopper 55 to the knob 212 and / or the proximal end portion 202, such as adhesives, mechanical means, etc., may be used.

[0035] Referring to Figures 5-5A and 5C-5E, the pretensioner rod 200 includes a concave section 220 to further facilitate bending of the pretensioner rod 200 through the tube 52 and to prevent or minimize its twisting while translating toward the pretensioner wheel 56 during the operation of the pretensioner. In particular, opposite the first recess 210 of the pretensioner rod 200, the concave section 220 defines a second recess 222 and extends in the longitudinal direction L. The concave section 220 extends along most of the entire length of the pretensioner rod 200. In one embodiment of the present disclosure, as shown in Figures 5, 5A, 5C, 5D, and 5E, the distal end portion 204 has a relatively larger or more complete cross-sectional area (i.e., a non-recessed section 224) for engaging with the pretensioner wheel 56 during translation, by which the recess 222 does not extend through the distal end portion 204, thereby reducing the amount of delamination of the pretensioner rod 200 that may occur at the initial contact with the pretensioner wheel 56, thereby improving the performance of the pretensioner system 44. In some embodiments, the non-recessed section 224 of the distal end portion 204 has a length of about 15 mm to about 25 mm, for example, about 20 mm (t y (See Figure 9A) The concave section 220 of the rod 200 may have a length of approximately 60 mm to approximately 145 mm.

[0036] Figures 5C to 5E show cross-sectional views of the pretensioner rod 200 at three different positions along the length of the rod 200 in Figure 5. Figure 5C shows a cross-sectional view of the distal end portion 204 of the rod 200, which has a non-concave section 224 and a concave portion 208 formed to have a first recess 210. Furthermore, the distal end portion 204 of the rod 200 has a side surface 228, which is formed to have a flat shape to reduce friction as the pretensioner rod 200 advances through the pretensioner tube 52 during translation inside the tube 52. Figure 5D shows a cross-sectional view of the central portion of the pretensioner rod 200, which has both a concave portion 208 formed to have a first recess 210 and a concave section 220 formed to have a second recess 222, in order to allow the pretensioner rod 200 to bend more easily across its radial thickness. The first recess 210 may be formed to have a groove, and the second recess 222 may be formed to have a flat shape. Figure 5E shows a cross-sectional view of the proximal end portion 202 of the rod having a non-recessed portion 206 and a recessed section 220.

[0037] Furthermore, as shown in Figure 5, the nearest end 203 has a relatively larger or more complete cross-sectional area for the stopper 55 to contact in order to reduce the initial compression amount on the pretensioner rod 200 during operation of the gas generator 36, by which the recesses / grooves 210 and 222 do not extend through the nearest end 203 of the rod 200, thereby improving the performance of the pretensioner system 44.

[0038] In Figures 5, 5A, and 5B, the pretensioner rod 200 includes a chamfered portion 216 disposed on a non-concave section 224 of the pretensioner rod 200 within the distal end portion 204. The chamfered portion 216 advantageously facilitates engagement between the pretensioner rod 200 and the pretensioner wheel 56 during pretensioning. The chamfered portion 216 is formed in a straight or curved shape, such as a concave shape, defining the chamfered surface. However, other shapes of the chamfered portion 216 may be implemented according to other exemplary embodiments. In Figure 5, for example, the straight shape of the chamfered portion 216 is configured to engage with the pretensioner wheel 56 during pretensioning, since the chamfered portion 216 on the pretensioner rod 200 is substantially parallel to the circumference of the pretensioner wheel 56 (see Figure 7B). Due to the tapered shape of the rod 200, the chamfered portion 216 of the pretensioner rod 200 can maintain clearance with the pretensioner wheel 56 (i.e., the space between the chamfered portion 216 of the rod 200 and the circumference of the pretensioner wheel 56) before pretension is applied.

[0039] As shown in Figures 5 to 5B, in some embodiments, the pretensioner rod 200 may further include another chamfered portion 218 (i.e., a second chamfered portion) on the distal end portion 204 of the rod 52, which may be tapered inward to form a chamfered shape along the length of the distal end 205 in the longitudinal direction L (not shown). The chamfered portion 218 is generally formed on the opposite side of the first chamfered portion 216 in the radial direction R of the pretensioner rod 200. In some embodiments, as shown in Figure 5, the second chamfered portion 218 may be formed to have a straight end face (i.e., not tapered) at the distal end 205 of the rod 200. Thus, the flat surface of the second chamfered portion 218 can advantageously reduce the force required to advance the pretensioner rod 200 within the tube 52, thereby facilitating the installation of the pretensioner rod 200 within the pretensioner system 44. However, according to another embodiment of the present invention, the second chamfered portion 218 may be tapered along the longitudinal direction L, similar to the first chamfered portion 216.

[0040] The pretensioner rod 200 is preferably made from a polymer material having reduced weight compared to the metal ball drive element of other rotary pretensioners. A specific polymer material can be selected to suit the user's specific requirements. The polymer material is preferably sufficiently flexible to allow for initial installation and to bend and flex through the pretensioner tube 52 in response to operation by the gas generator 36. The polymer material is preferably sufficiently rigid to be pushed through the tube 52 in response to operation, thereby allowing the rod 200 to adequately transmit the load to the pretensioner wheel 56 of the pretensioner system 44.

[0041] Furthermore, the pretensioner rod 200 is preferably made of a deformable polymer material. During and after operation, the rod 200 deforms in response to the operation and contact with other components of the pretensioner system 44. Thus, due to the vanes 102 of the pretensioner wheel 56, the pretensioner rod 200 deforms (elastically and plastically) without any significant material separation (breaking) of the rod 200, thereby the load applied by the operating gas pressure of the system 44 is fully transmitted to the pretensioner wheel 56 through the deformation of the pretensioner rod 200. This deformation is discussed further below with reference to the use of the system 44, where the plastic deformation locks the system to prevent or limit the retraction of the rod 200 without relying entirely on the maintained gas pressure in the system. The plastic deformation also allows the rod 200 to deform and engage with the vanes of the pretensioner wheel 56. Alternatively, the pretensioner rod 200 may be made from a nylon thermoplastic material. The rod 200 may also be made from an aliphatic polyamide thermoplastic material. Alternatively, the rod 200 may be made from a similar thermoplastic material, such as an acetal material or a polypropylene material.

[0042] Referring to Figure 6, the pretensioner wheel 56 includes a body portion 100 having a substantially annular shape. The pretensioner wheel 56 is configured to be rotatably coupled to the spindle 40 on one side 110 to operably connect the pretensioner wheel 56 to the spindle 40, and to be configured to operably engage with the spring end cap 42 on the other side 112. As shown in Figures 4 and 6, the pretensioner wheel 56 includes a plurality of vanes 102 that each project radially from the body portion 100, the vanes 102 extending from the center of the body portion 100. Furthermore, as shown in Figure 6, the pretensioner wheel 56 further includes a flange 108 for guiding the pretensioner rod 200 when the rod 200 engages with the plurality of vanes 102 of the pretensioner wheel 56. The flanges 108 of the pretensioner wheel 56 extend further radially from the body portion 100 on both sides 110 and 112 compared to the radially outer tip 106 of the vane 102. Thus, the vane 102 extends between the pair of flanges 108 along a radius extending from the central axis X of rotation of the body portion 100. In addition, the flanges 108 prevent the engaged rod 200 on the vane 102 of the pretensioner wheel 56 from being disengaged laterally.

[0043] In Figure 6, each of the vanes 102 can have a uniform size and shape and can be uniformly distributed around the pretensioner wheel 56. Each vane 102 has a substantially triangular shape on the cross-sectional plane of the pretensioner wheel 56 perpendicular to the central axis X and has a root section 114 that tapers toward the tip 106 as the vane 102 extends radially outward from the body portion 100 (see Figure 8). The specific width and pitch of the vanes 102 can be selected as desired. Multiple vanes 102 are combined to form a hemispherical cavity 104 disposed between two adjacent vanes 102. Furthermore, each cavity 104 formed between two adjacent vanes 102 has a pocket 138 preferably formed as a U-shape. However, the pocket shape of the cavity 104 can be modified according to another embodiment of the present disclosure. Furthermore, the U-shaped bottom section of pocket 138 is formed in a semi-circular or rounded shape. Generally, the radius range of the rounded U-shape is 3 mm to 7 mm, and preferably the radius of the U-shape is 5 mm.

[0044] Figure 7A shows a conventional pretensioner system having a second tube end of a pretensioner tube with a pretensioner wheel, and Figure 7B shows a detailed view of the second tube end 53 (i.e., outlet region) of a pretensioner tube 52 having a pretensioner wheel 56 according to the present disclosure. A polymer rod 200 is inserted into the tube 52, and the distal end portion 204 of the polymer rod 200 is located at the second tube end 53 of the pretensioner tube 52 before pretension is applied (i.e., in the pre-operation state of the gas generator). In the pretensioner system 44, the polymer rod 200 inserted into the tube 52 may change its dimensions when the temperature of the environment in which the pretensioner system is generally used fluctuates, such as from high daytime temperatures to low nighttime temperatures, or between summer and winter (i.e., the polymer rod extends itself along its longitudinal direction L). Therefore, since the polymer material of the pretensioner rod 200 has a higher coefficient of linear thermal expansion than the pretensioner tube 52 formed from steel material, the polymer rod 200 inside the tube 52 has a larger dimensional change than the tube 52. As shown in Figure 7A of a conventional pretensioner system, the polymer rod may move in the direction of lower frictional resistance after a high-temperature-low-temperature cycle, which is defined as thermal creep that can cause the polymer rod to move out of the tube (see the second tube end of the pretensioner tube in Figure 7A). As shown in Figure 7A, if thermal creep causes the polymer rod to move out of the tube (i.e., to retract from the tube), the polymer rod may interfere with other components of the pretensioner system 44, such as the pretensioner wheel 56, which may lock up in the pre-operation state due to interference by the polymer rod 200.

[0045] Figure 7B shows an exemplary embodiment of the present disclosure having a creep prevention function. As shown in Figure 7B, the pretensioner tube 52 includes a tube retainer 50 formed radially inward at the second tube end 53 of the tube 52 (i.e., the exit region, see Figure 4A), and the pretensioner rod 200 includes a projection 226 projecting radially outward from a first recess 210 in a concave portion 208 (see Figure 5B) of the distal end portion 204 of the rod 200. As shown in Figure 7B, when thermal creep occurs in the polymer rod 200 (i.e., the dimensions of the polymer rod increase along the longitudinal direction of the rod), the projection 226 of the polymer rod 200 interferes with the tube retainer 50 of the pretensioner tube 52, so that the polymer rod 200 moving out of the tube 52 can be restricted (or avoided) in the pre-operation state. Therefore, the projection 226 of the rod 200 connected to the tube stopper 50 of the tube 52 can limit how far the polymer rod 200 can advance due to thermal creep of the rod 200. Thus, as shown in Figure 7B, the space defined between the periphery of the pretensioner wheel 56 and the surface of the chamfered portion 216 formed on the distal end portion 204 of the polymer rod 200 is sufficient for the pretensioner wheel 56 to rotate freely without interfering with the rod 200.

[0046] Furthermore, creep prevention mechanisms such as the projection 226 on the polymer rod 200 and the tube stopper 50 on the tube 52 can also be used as installation support parts for the pretensioner rod 200 to position the most distal end 205 of the polymer rod 200 in a more precise position within the pretensioner tube 52. In addition, the projection 226 on the polymer rod 200 is designed to be sheared or scraped off by the pretensioning force generated by the gas generator 36 in the pretensioner system 44 when pretensioning is initiated (i.e., in the post-operation state). Thus, in the post-operation state, the pretensioner rod 200 can move freely out of the pretensioner tube 52 without interference between the projection 226 on the rod 200 and the pretensioner tube 52.

[0047] Referring to Figure 8, the pretensioner wheel 56 is formed to have an odd number of vanes 102, ranging from 5 to 13. For example, the pretensioner wheel 56 is preferably formed to have 11 vanes. However, the number of vanes 102 is adjusted according to the desired load and size of the pretensioner system 44. As shown in Figure 8, when the pretensioner wheel 56 is formed to have 11 vanes, the vanes 102 are evenly spaced along the circumference of the pretensioner wheel 56 at intervals of approximately 32.73 degrees. Thus, the arrangement of the odd number of vanes 102 is configured to avoid pinch points when the pretensioner wheel 56 rotates and engages with the pretensioner rod 200. That is, the odd number of vanes 102 prevents the pretensioner wheel 56 from locking due to a deformed pretensioner rod 200 when the pretensioner rod 200 engages with the pretensioner wheel 56. This is because, in an odd number of vanes, there are no vanes that are opposite each other in the diametrical direction, both of which are compressing the polymer rod. Furthermore, each of the vanes 102 forms a first side wall 116 and a second side wall 118 such that they form a triangle in cross-section, as shown in Figure 8.

[0048] Furthermore, Figure 8A shows a detailed cross-sectional view of the pretensioner wheel 56. In Figures 8 and 8A, the root circle 132 of the pretensioner wheel 56 is defined by connecting each of the root sections 114 of the vane 102, and the diameter of the root circle 132, D r In exemplary embodiments, the diameter of the tip circle 134 of the pretensioner wheel 56 is 28.35 mm. In addition, the tip circle 134 of the pretensioner wheel 56 is defined by connecting each tip 106 of the vanes 102, and the diameter of the tip circle 134 (tip diameter, D t In an exemplary embodiment, the diameter of the intermediate circle is 38.4 mm. Furthermore, in Figure 8, an intermediate circle 140 is defined so as to be located between the root circle 132 and the tip circle 134, thereby the diameter of the intermediate circle 140 (intermediate diameter, D m ) is D m =D r+1 / 2(D t -D r ) and the like are determined by mathematical expressions. However, the specific dimensions of the pretensioner wheel 56 described above are modified according to other aspects of the present disclosure.

[0049] As shown in FIG. 8A, on the first side wall 116 and the second side wall 118 of the vane 102, the first point P a and the second point P b are each defined to be located at a position where the intermediate circle 140 intersects each surface of the first side wall 116 and the second side wall 118. The first point P a is located at the intersection position with the intermediate circle 140 on the surface of the first side wall 116, and the second point P b is located at the intersection position with the intermediate circle 140 on the surface of the second side wall 118. Further, as shown in FIG. 8A, the vane distance P ab is defined between the first point P a and the second point P b within the pocket 138 of each vane 112.

[0050] Furthermore, FIG. 8B shows a detailed cross-sectional view of the pretensioner rod 200 that exits the pretensioner tube 52 to engage with the pretensioner wheel 56 during pretensioning. As shown in FIG. 5, the pretensioner rod 200 has a first chamfered portion 216 that is tapered with respect to a flat shape at the distal end portion 204 of the pretensioner rod 200 to engage with the pretensioner wheel 56 during pretensioning. As shown in FIG. 8B, the chamfered portion 216 of the pretensioner rod 200 has a starting point X a that is located slightly above the center line of the rod 200 along the longitudinal direction L such that the chamfered portion 216 of the rod 200 is tapered with respect to a flat surface, b and an end point X that is located on the circumferential line of the rod 200. Further, the chamfered portion length X ab is defined as the distance between the starting point X a and the end point X b and may be a straight line or a curve in the side cross-sectional view of the rod 200. In addition, as shown in FIGS. 8A and 8B, the chamfered portion length X of the chamfered portion 216ab To avoid pretensioner rod detachment and reduce energy consumption during pretensioning, the vane distance P of vane 102 is used. ab It is larger than that.

[0051] Figure 9A shows a detail view of the distal end portion 204 of the pretensioner rod 200 in Figure 5, and Figure 9B shows a detail view of the pretensioner rod 200 engaged with the pretensioner wheel 56. Referring again to Figure 7B, the distal end portion 204 of the pretensioner rod 200 is located at the exit of the pretensioner tube 52, and the surface of the chamfered portion 216 is positioned substantially parallel to the circumference of the annular body portion 100 of the pretensioner wheel 56. During pretensioning, as the pretensioner rod 200 exits the tube 52 toward the pretensioner wheel 56, the rod 200 moves along the pretensioning direction P and engages with the vanes 102 of the pretensioner wheel 56. Therefore, when the pretensioner rod 200 is fully extended out of the tube 52 and coupled with the pretensioner wheel 56, the pretensioner rod 200 engages with the vanes 102 of the pretensioner wheel 56, thereby applying pretension to the pretensioner system 44.

[0052] As shown in Figures 9A and 9B, when the pretensioner rod 200 engages with the pretensioner wheel 56, the pretensioner rod 200 deforms in accordance with the engaged vane 102 and cavity 104. In order to engage the pretensioner rod 200 with the pretensioner wheel 56 and transmit pretension force or torque, the pretensioner wheel 56 is generally made of a material having higher hardness than the material of the pretensioner rod 200, such as glass fiber reinforced plastic or metal. Thus, as shown in Figure 9B, the pretensioner rod 200 deforms or dents along the vane 102 and deforms to fill the cavity 104.

[0053] In Figures 9A and 9B, the pretensioner rod 200 has a non-concave section 224 that is thicker than the main body portion of the rod 200 (i.e., the concave section 220) due to the recess 222. In a side view of the pretensioner rod 200 along the longitudinal axis L (see Figures 5 and 9A), the radial thickness t of the non-concave section 224 is shown. x The thickness of the concave section 220 is t b It is larger than that. Furthermore, the length t of the non-concave section 224 of the rod 200 y This is the two adjacent wheel tip ends T x The distance is greater than that, thereby, during pretension, the rod 200 effectively engages with the vanes 102 of the pretensioner wheel 56. Because the distal end portion 204 of the rod 200 is thicker, the pretensioner rod 200 maintains engagement with the pretensioner wheel 56 without peeling and / or cutting, and also reduces energy consumption when the pretensioner rod 200 is deformed while applying pretension. Thus, since the pretensioner rod 200 can engage with the pretensioner wheel 56 without any peeling or cutting of the rod material, the load applied by the gas pressure can be fully transmitted to the pretensioner wheel 56.

[0054] Furthermore, due to the vanes 102 of the pretensioner wheel 56, as shown in Figure 9B, the deformation shape of the rod 200 is similar to that of the vanes 102. Therefore, the overlapping portion between the rod 200 and the vanes 102 (i.e., the deformation depth d of the rod 200) is approximately 15% to 50% of the radial thickness of the rod 200 in the radial direction of the pretensioner wheel 56. Thus, the deformation depth d is less than half the radial thickness of the pretensioner rod 200. As shown in Figure 9B, when the pretensioner rod 200 is engaged with the pretensioner wheel 56 during pretensioning, the pretensioner rod 200 maintains its engagement with the pretensioner wheel 56 without any separation (cutting or peeling) of the material of the pretensioner rod 200.

[0055] Referring again to Figures 4 and 4A, as described above, the retractor assembly 32 includes a gas generator 36 that provides an expanding gas in response to an ignition signal. The expanding gas increases the pressure in the tube 52, which eventually pushes the rod 200 away from the gas generator 36 and through the tube 52. In Figure 4, the pretensioner tube 52 includes a piston or seal 72. The seal 72 may have a cylindrical shape with a cylindrical outer surface, as best shown in Figure 4. However, other suitable shapes of the piston or seal 72 may be implemented according to other embodiments of the present disclosure. When the gas generator 36 is activated, the seal 72 is made capable of resisting gas leakage. The pressurized gas in the gas chamber 74 expands the seal 72, which helps prevent gas from leaking beyond the seal 72. Thus, the seal 72 of the present disclosure is operable to maintain a high sealing pressure and maintain residual gas pressure in the tube 52.

[0056] The seal 72 is formed, for example, in a spherical shape. The seal 72 is slidably disposed within the tube 52 and is operable to drive the pretensioner rod 200 along an operating path along the tube 52. As will be understood by those skilled in the art, the seal 72 may be press-fitted into the tube 52 or otherwise fitted. In addition, the seal 72 may be made of a variety of materials known in the art, such as any suitable plastic or polymer (e.g., polyester, rubber, thermoplastic resin, or other elastic or deformable material), which defines a generally elastic structure. Furthermore, the seal 72 may be die-cast, forged, or molded from metal, plastic, or other suitable material. According to a further aspect of this disclosure, the seal 72 may be formed using a two-cavity or two-shot (2K) injection molding process. This generally elastic structure allows the shape of the seal 72 to change slightly in response to pressure, thereby improving the sealing provided by the piston.

[0057] While the above description constitutes a preferred embodiment of the present invention, it will be understood that the present invention can be modified, altered, and changed without departing from the appropriate scope and fair meaning of the appended claims.

Claims

1. A seat belt pretensioner system for use in a seat belt pretensioner retractor assembly (32), wherein the seat belt pretensioner system (44) is A pretensioner tube (52) that is in fluid communication with a gas generator (36), A pretensioner rod (200) comprising a proximal end portion (202) disposed toward the gas generator (36) and a distal end portion (204) disposed toward the outlet region of the pretensioner tube (52), wherein the pretensioner rod (200) disposed inside the pretensioner tube (52) is defined as the pre-operation state, and the pretensioner rod (200) adapted to move toward the pretensioner wheel (56) inside the pretensioner tube (52) when the gas generator (36) is activated is defined as the post-operation state, A seat belt pretensioner system characterized in that the pretensioner rod (200) is coupled to the pretensioner tube (52) and includes a projection (226) formed radially on the rod (200) to restrict the rod (200) from moving out of the pretensioner tube (52) in the pre-operation state.

2. The seat belt pretensioner system according to claim 1, further characterized in that the pretensioner tube (52) includes a tube stopper (50) formed radially inward in the outlet region of the tube (52) for engaging with the projection (226) formed on the distal end portion (204) of the pretensioner rod (200).

3. The seat belt pretensioner system according to claim 1 or 2, further characterized in that, in the pre-operation state, when thermal creep occurs in the rod (200), the movement of the pretensioner rod (52) toward the pretensioner wheel (56) is restricted by the interaction between the projection (226) and the tube return stopper (50).

4. The seat belt pretensioner system according to any one of claims 1 to 3, further characterized in that the projection (226) of the pretensioner rod (200) is designed to be sheared or rubbed off by the pretensioning force generated by the gas generator (36), thereby allowing the pretensioner rod (200) to move freely out of the pretensioner tube (52) in the post-operation state.

5. A seat belt pretensioner system according to any one of claims 1 to 3, further characterized in that, due to the tube stopper (50) of the pretensioner tube (52), the projection (226) of the pretensioner rod (200) engages with the tube stopper (50), thereby causing the distal end (205) of the rod (200) to be substantially aligned with the second tube end (53) of the pretensioner tube (52) in the pre-operation state.

6. The seat belt pretensioner system according to any one of claims 1 to 5, further characterized in that the projection (226) of the pretensioner rod (200) protrudes radially from the concave portion (208) of the pretensioner rod (200).

7. The seat belt pretensioner system according to any one of claims 1 to 6, further characterized in that the pretensioner rod (200) is in the form of a flexible, elongated rod formed from a polymer material.

8. A seat belt pretensioner system for use in a seat belt pretension retractor assembly (32) having a housing (54) and a spindle (40), wherein the seat belt pretensioner system (44) is A pretensioner tube (52) that is in fluid communication with a gas generator (36), A pretensioner rod (200) having a proximal end portion (202) disposed toward the gas generator (36) and a distal end portion (204) disposed inside the pretensioner tube (52) at the outlet of the pretensioner tube (52), wherein the pretensioner rod (200) has a chamfered portion (216) formed on the distal end portion (204) of the pretensioner rod (200), A pretensioner wheel (56) is rotatably mounted to the housing (54) and fixedly coupled to the spindle (40), wherein the pretensioner wheel (54) includes an annular body portion (100) and a plurality of vanes (102) formed around the circumference of the body portion, and each of the plurality of vanes (102) has a first side wall (116) and a second side wall (118), and the pretensioner wheel (56) comprises In a cross-section of the pretensioner wheel (56) perpendicular to the axis of rotation of the pretensioner wheel (56), the pretensioner wheel (56) has a root circle (132) defined by connecting each of the root sections (114) of the vanes (102), and a tip circle (134) defined by connecting each of the tip points (106) of the vanes (102). A first point (Pa) is defined on the surface of the first side wall (116) when the circular line defined between the tip circle (134) and the root circle (132) intersects with the first side wall (116), and a second point (Pb) is defined on the surface of the second side wall (118) when the circular line intersects with the second side wall (118), thereby defining a vane distance (Pab) between the first point and the second point in the pocket (138) formed between the two vanes (102). A seat belt pretensioner system characterized in that the chamfered portion (216) of the pretensioner rod (200) has a chamfered portion length (Xab) that is greater than the vane distance (Pab) within the pocket (138).

9. The seat belt pretensioner system according to claim 8, further characterized in that, in a side cross-sectional view of the rod (200) along the longitudinal axis, the chamfered portion (216) is tapered, has a starting point on the farthest end (205) of the rod (200) above the center line of the rod along the longitudinal axis, and has an ending point on the peripheral edge of the rod (200), thereby defining the length of the chamfer as the distance from the starting point to the ending point.

10. The seat belt pretensioner system according to claim 8 or 9, further characterized in that the chamfered portion (216) of the rod (200) is formed to have a flat or curved shape.

11. The seat belt pretensioner system according to any one of claims 8 to 10, further characterized in that the circular line is defined as an intermediate circle (140) located between the tip circle (134) and the base circle (132).

12. The seat belt pretensioner system according to any one of claims 8 to 11, further characterized in that the pretensioner rod (200) is configured to avoid peeling of the rod (200) and to reduce energy consumption when the rod deforms during pretensioning.

13. The seat belt pretensioner system according to any one of claims 8 to 11, further characterized in that, in a side cross-sectional view of the rod (200) along the longitudinal axis, the first radial thickness defined in the non-concave section (224) of the rod (200) is greater than the second radial thickness defined in the concave section (220) of the rod (200).

14. The seat belt pretensioner system according to any one of claims 8 to 13, further characterized in that the length of the non-concave section (224) of the rod (200) along the longitudinal axis is greater than the tip distance between two adjacent vane tips of the pretensioner wheel (56).

15. A seat belt pretensioner system according to any one of claims 8 to 13, further characterized in that, when the pretensioner rod (200) is engaged with the vane (102) of the pretensioner wheel (56) during pretensioning, the deformation depth (d) of the pretensioner rod (200) is 15% to 50% of the radial thickness of the rod (200).

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