Piston, seat belt retractor and pretensioning seat belt

Abstract

A piston (60) for a pretensioning seat belt. The piston comprises: a piston seat (61), which comprises a front surface and a first recess (613) recessed from the front surface; and a piston head (62), which is assembled on the front side of the piston seat (61) and comprises an abutting face (622) abutting against the front surface, wherein a second recess (621) is arranged in the front side of the piston head. The piston (60) is provided with a pressure control mechanism, wherein the pressure control mechanism is configured to: block, when the gas pressure of the rear side of the piston seat (61) is less than a preset value, an airflow from flowing forwards; and form an airflow channel when the gas pressure of the rear side of the piston seat (61) is greater than or equal to the preset value, the airflow channel being suitable for deflecting the airflow and allowing the airflow to flow towards the front of the piston (60). The piston can realize pressure relief under abnormal working conditions while having good sealing characteristics, and has a simple structure, is convenient to manufacture and involves relatively low costs. A seat belt retractor and a pretensioning seat belt are further comprised.

Description

Piston, seat belt retractor and pre-tensioned seat belt Technical Field

[0001] The present invention generally relates to the field of vehicle passive safety devices, and more particularly, to a piston for a pre-tensioned seat belt. In addition, the present invention also relates to a seat belt retractor including such a piston, and to a pre-tensioned seat belt including such a seat belt retractor. Background Art

[0002] The gap between the webbing and the wearer, reduced by the spring retraction force of a non-pretensioned seat belt retractor, is insufficient. Furthermore, clothing is thick, and these gaps can significantly impact the safety of vehicle occupants in an emergency. With the advancement of science and technology, people's requirements for vehicle occupant protection continue to increase, leading to an increasing demand for pretensioned seat belts.

[0003] For pre-tensioned seatbelts, the pre-tensioner can release high energy in the retractor before or after an emergency occurs, instantly tightening the webbing with a greater force that the occupant can withstand. This further reduces the gap between the webbing and the occupant's body and confines the occupant to the designed position, thereby coordinating with the subsequent activation of the airbag for protection. The basic working principle of the pre-tensioner is that when the gas generator is triggered, the high-pressure airflow generated passes through the piston and transmission medium, causing the reel in the seatbelt retractor to rotate, thereby instantly tightening the webbing to restrain the occupant in the seat. At the same time, under abnormal operating conditions, such as when the gas pressure is too high, in order to protect other components of the pre-tensioner, the piston in the pre-tensioner can release pressure for decompression.

[0004] Patent document WO2017 / 021494A1 discloses a seal with internal pressure relief function for a seat belt retractor, in which a set of metal parts subassemblies are embedded in the seal, and the bottom is supported by metal parts and pre-tightening balls. Internal pressure relief is achieved by rupturing the center metal cap. However, the assembly has many parts, the assembly process is complex, and the quality cost is high.

[0005] Patent document EP3059137A1 also discloses a seal with internal pressure relief function for a seat belt retractor, wherein the internal pressure relief is achieved by directly opening a hole in the center of the seal. The seal and the bottom support are arranged separately, and the bottom support is provided with an air relief hole. However, this opening method affects the strength of the seal and also affects the preload performance.

[0006] Summary of the Invention

[0007] The present invention aims to provide a piston for a pretensioner seat belt that overcomes at least one of the aforementioned drawbacks of the prior art. More specifically, the piston provides excellent sealing performance while enabling pressure relief under abnormal operating conditions. Furthermore, the piston has a simple structure, is easy to manufacture, and is relatively inexpensive.

[0008] To this end, a first aspect of the present invention provides a piston for a pretensioned seat belt, comprising: a piston seat including a front surface and a first recessed portion recessed from the front surface; and a piston head assembled to the front side of the piston seat and including an abutting surface abutting the front surface, wherein the front side of the piston head is provided with a second recessed portion adapted to support a transmission member. The piston is provided with a pressure control mechanism configured to: block forward airflow when the gas pressure behind the piston seat is less than a preset value; and to form an airflow channel when the gas pressure behind the piston seat is greater than or equal to the preset value, wherein the airflow channel is adapted to deflect the airflow and allow the gas to flow toward the front of the piston.

[0009] According to an optional embodiment of the present invention, the piston seat includes at least one assembly portion protruding from the front surface, and the piston head includes an assembly groove snap-fitted with the at least one assembly portion.

[0010] According to an optional embodiment of the present invention, a third recess is provided on the rear side of the piston seat, and the third recess includes a middle part and an edge part located outside the middle part, the middle part defines an assembly surface suitable for fitting an assembly tool, and the edge part is recessed from the edge of the assembly surface to form an annular edge suitable for radially outward deformation.

[0011] According to an optional embodiment of the present invention, the assembly surface is a curved surface.

[0012] According to an optional embodiment of the present invention, the pressure control mechanism is constructed to include: a first channel inlet recessed from the bottom of the middle part; a first channel outlet recessed from the bottom of the first recess; and a barrier portion located between the first channel inlet and the first channel outlet, wherein the barrier portion is configured to rupture to connect the first channel inlet and the first channel outlet when the gas pressure in the third recess is greater than or equal to the preset value.

[0013] According to an optional embodiment of the present invention, the pressure control mechanism is constructed to include: a first channel connecting the middle part and the first recess; and a barrier member arranged in the first channel, wherein the barrier member is configured to close the first channel when the gas pressure in the third recess is less than the preset value, and to rupture to open the first channel when the gas pressure in the third recess is greater than or equal to the preset value.

[0014] According to an optional embodiment of the present invention, the pressure control mechanism further comprises at least one second channel defined by the piston head, wherein the at least one second channel is configured to guide the airflow in the first recess from the abutting surface to the side wall surface of the piston head.

[0015] According to an optional embodiment of the present invention, the piston head includes a support portion protruding from the abutment surface and abutting against the first recess, and the pressure control mechanism also includes at least one second channel defined by the piston head, and the at least one second channel is configured to guide the airflow in the first recess from the support portion to the side wall surface of the piston head.

[0016] According to an optional embodiment of the present invention, the first recess connects the front surface and the middle part, and the piston head includes a support portion protruding from the abutment surface and abutting against the inner wall of the first recess, wherein the pressure control mechanism includes: a first channel defined by the support portion, the first channel being configured to be closed when the gas pressure in the third recess is less than the preset value, and to be opened when the gas pressure in the third recess is greater than or equal to the preset value to guide the airflow from the third recess to the position of the abutment surface; and at least one second channel, the at least one second channel being configured to communicate with the first channel and guide the airflow from the position of the abutment surface to the side wall surface of the piston head.

[0017] According to an optional embodiment of the present invention, the pressure control mechanism is configured such that an angle between a direction of the air flow output from the air flow channel and an axial direction of the piston is between 20° and 90°.

[0018] According to an optional embodiment of the present invention, the piston seat is made of a first plastic material, and the piston head is made of a second plastic material having a harderness greater than that of the first plastic material.

[0019] The second aspect of the present invention provides a seat belt retractor, comprising: a bracket; a reel assembly rotatably assembled to the bracket, the reel assembly comprising a reel suitable for winding a webbing and a gear fixedly connected to the reel; a pre-tensioning pipe assembled to the bracket; a gas generator assembled in the pre-tensioning pipe; and at least one piston according to the first aspect of the present invention and at least one transmission member arranged in the pre-tensioning pipe, the piston being arranged between the gas generator and the transmission member, and the piston seat having an interference fit with the inner wall of the pre-tensioning pipe, the seat belt retractor is configured to generate an airflow when the gas generator is ignited to push the piston and the transmission member to move in the pre-tensioning pipe, so that the transmission member interacts with the gear and drives the reel to rotate.

[0020] A third aspect of the present invention provides a pre-tensioned seat belt comprising the seat belt retractor according to the second aspect of the present invention.

[0021] Compared with the prior art, the piston for pre-tensioned seat belts according to the present invention has several advantages, in particular: a seat belt retractor with such a piston can quickly tighten the gap between the webbing and the occupant to restrain the occupant in the event of a vehicle collision, wherein the good sealing properties of the piston enable full energy utilization, reduce the amount of gunpowder used, and improve the efficiency of the pre-tensioning function. At the same time, a pressure control mechanism is provided in the piston in a simple and low-cost manner, so that abnormal pressure can be released through the control structure to protect other components of the seat belt, and flames can be suppressed and gas jet energy can be reduced during release. In addition, the piston has a simple structure, is easy to assemble, and has a low cost, and can be widely used in various types of seat belt retractors. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Other features and advantages of the present invention will be better understood through the following detailed description of preferred embodiments in conjunction with the accompanying drawings. In the accompanying drawings, the same reference numerals represent the same or similar components.

[0023] FIG1 is a perspective view of a seat belt retractor according to an embodiment of the present invention;

[0024] FIG2 is a cross-sectional view of the seat belt retractor in FIG1 at the gear position of the pretensioning device;

[0025] FIG3 is a cross-sectional view of a pre-tightening pipe of the pre-tightening device of the seat belt retractor in FIG1 ;

[0026] 4A to 4D are respectively a perspective view, an exploded view, a side view and a cross-sectional view of a piston according to a first embodiment of the present invention;

[0027] 5A to 5D are respectively a perspective view, an exploded view, a side view and a cross-sectional view of a piston according to a second embodiment of the present invention;

[0028] 6A to 6D are respectively a perspective view, an exploded view, a side view and a cross-sectional view of a piston according to a third embodiment of the present invention;

[0029] 7A to 7D are respectively a perspective view, an exploded view, a side view and a cross-sectional view of a piston according to a fourth embodiment of the present invention;

[0030] 8A to 8D are respectively a perspective view, an exploded view, a side view and a cross-sectional view of a piston according to a fifth embodiment of the present invention.

[0031] The elements in the drawings are shown for simplicity and clarity and are not necessarily drawn to exact scale. It should be understood that the drawings are not only used to explain and illustrate the present invention but also to help define the present invention when necessary. DETAILED DESCRIPTION

[0032] The following detailed discussion of how to make and use specific embodiments is provided. However, it should be understood that the specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and are not intended to limit the scope of the invention.

[0033] As shown in Figures 1 to 3, the present invention relates to a seat belt retractor for a pre-tensioned seat belt, which mainly includes a bracket 10, a reel assembly 20, a pre-tensioning pipe 30, an outer cover 40, a gas generator 50, at least one piston 60 and at least one transmission member, such as the pre-tensioning ball 70 shown.

[0034] The bracket 10 is configured, for example, as a U-shaped bracket and is fixed to a vehicle seat. The reel assembly 20 is rotatably mounted on the bracket 10 and includes a reel 21 for winding a webbing and a gear 22 fixedly connected to the reel 21. For example, a splined shaft is provided at one axial end of the reel 21. The gear 22 is non-rotatably mounted on this splined shaft, allowing it to rotate with the reel 21. The gear 22 has a toothed portion with a special meshing pattern that mates with a transmission element. A cover 40 is mounted on the bracket 10 to cover the axial end of the reel 21.

[0035] The pretensioning pipe 30 is mounted on the bracket 10 and is configured, for example, as a serpentine pipe. The gas generator 50 is assembled into the pretensioning pipe 30 at one end, for example, by riveting. A piston 60 and a plurality of pretensioning balls 70, serving as transmission elements, are housed and retained within the pretensioning pipe 30. The piston 60 is positioned between the gas generator 50 and the pretensioning balls 70 and forms an interference fit with the inner wall 31 of the pretensioning pipe 30. Thus, the pretensioning pipe 30, gas generator 50, piston 60, pretensioning balls 70, and gear 22 constitute the pretensioning device of the seatbelt retractor.

[0036] In an emergency, the gas generator 50 is ignited to generate a high-temperature, high-pressure airflow, which in turn propels the piston 60 and the preload ball 70 within the preload pipe 30. The outlet of the preload pipe 30, opposite the gas generator 50, is aligned with the teeth of the gear 22. Upon exiting the preload pipe 30, the preload ball 70 engages with the shaped meshing portion of the gear 22 teeth, thereby rotating the gear 22 and the reel 21, instantly tightening the webbing. The shaped meshing portion of the gear 22 teeth can, for example, be configured as a ball-and-socket to ensure smooth meshing between the preload ball 70 and the gear 22.

[0037] The following describes a specific embodiment of the piston 60 with reference to Figures 4A to 8D . In this specification, the front side of the piston 60 is the side facing the preload ball 70, and the rear side of the piston 60 is the side facing the gas generator 50. Furthermore, in this specification, unless otherwise specified, the terms "axial" and "radial" refer to both the axial and radial directions of the piston 60.

[0038] First embodiment

[0039] As shown in Figures 4A to 4D, the piston 60 includes a piston seat 61 and a piston head 62 assembled to the front side of the piston seat 61. The piston seat 61 can function as a seal. More specifically, when the gas generator 50 is ignited, the gas pressure applied to the rear side of the piston seat 61 can cause the piston seat 61 to deform, tightening the gap between the piston seat 61 and the inner wall 31 of the preload pipe 30, thereby achieving a sealing effect.

[0040] The front side of the piston seat 61 includes a front surface 611, a first recessed portion 613 recessed rearwardly from the front surface 611, and at least one mounting portion 612 protruding from the front surface 611, such as three mounting portions 612 evenly distributed circumferentially on the front surface 611 as shown. Correspondingly, the piston head 62 includes an annular mounting groove 624 recessed radially inwardly from its sidewall surface 623 (i.e., the surface facing the inner wall 31 of the preload conduit 30), which engages with a protrusion on each mounting portion 612, thereby securely mounting the piston head 62 to the front side of the piston seat 61 and ensuring that the abutting surface 622 of the piston head 62 (i.e., the rear surface of the piston head 62) closely abuts the front surface 611 of the piston seat 61. It will be understood that the above-described mounting method of the piston seat 61 and the piston head 62 is not restrictive, and the shape, position, and mounting method of the mounting portions of both can be modified according to actual needs.

[0041] The front side of the piston head 62 is provided with a second recess 621 for supporting the transmission member. This second recess 621, for example, defines an arcuate surface for supporting and pushing the preload ball 70. Specifically, this surface is spherical, for example, with a spherical surface characteristic of 10%-45%, so that the second recess 621 forms a surface contact with the preload ball 70. Furthermore, this arcuate surface may also be provided with multiple protrusions to ensure multi-point, center-symmetrical contact between the second recess 621 and the preload ball 70. The overall radial dimension of the piston head 62 should account for 20%-100% of the cross-sectional area of ​​the preload conduit 30.

[0042] The rear side of the piston seat 61 is provided with a third recessed portion facing the gas generator 50. This third recessed portion includes a middle portion 615 and an edge portion 614 located outside the middle portion 615. The middle portion 615 defines a mounting surface 6151, which is, for example, configured as an arcuate surface (e.g., a spherical surface or other curved surface) to conform to the outer contour of an assembly tool. This facilitates the assembly tool to hold the piston 60 via the mounting surface 6151 and install it into the preloaded pipe 30. The edge portion 614 is recessed outward from the edge of the mounting surface 6151 to form a tail ring edge 6141 of the piston 60. Therefore, when assembling the piston 60, the uneven transition between the inner wall surface 6142 of the ring edge 6141 and the mounting surface 6151 prevents the assembly tool from contacting the ring edge 6141 and causing wear. Furthermore, due to the relatively small thickness of the annular edge 6141, when the gas generator 50 is ignited, the airflow within the third recess of the piston seat 61 can push the annular edge 6141 to expand and deform radially outward, allowing the outer wall surface of the annular edge 6141 to more closely adhere to the inner wall 31 of the preload pipe 30 than other outer wall portions of the piston seat 61, thereby further improving sealing. It will be appreciated that the inner wall surface 6142 of the annular edge 6141 can be either flat or curved, and this is not a limitation of the present invention.

[0043] According to this first embodiment, the pressure control mechanism of the piston 60 includes a first channel inlet 616 recessed forward from the bottom of the middle portion 615 of the third recess of the piston seat 61, a first channel outlet 617 recessed rearward from the bottom of the first recess 613 of the piston seat 61, and a barrier 618 located between the first channel inlet 616 and the first channel outlet 617. More specifically, the first channel inlet 616 and the first channel outlet 617 have reduced radial dimensions compared to the middle portion 615 and the first recess 613 and are separated by the barrier 618; the barrier 618 itself, as an integral part of the piston seat 61, constitutes a diaphragm-like structure in the piston seat 61 that can rupture at preset pressures and temperatures. Therefore, when the gas pressure on the rear side of the piston seat 61 (i.e., the gas pressure in the third recess) is less than a preset value, the barrier portion 618 can block the airflow from flowing forward; and when the gas pressure on the rear side of the piston seat 61 is greater than or equal to the preset value, due to the setting of the first recess 613, the rear part of the piston seat 61 is more likely to undergo radial inward contraction and deformation, and the barrier portion 618 can thus easily rupture to connect the first channel inlet 616 and the first channel outlet 617, thereby forming a first channel, so that the airflow on the rear side of the piston seat 61 can reach the first recess 613 via the first channel.

[0044] The pressure control mechanism of the piston 60 further includes at least one second channel 625, for example, one to eight second channels 625, defined by the piston head 62. These second channels 625 are, for example, grooves defined along the edge of the piston head 62. The grooves extend from the abutment surface 622 of the piston head 62 to the sidewall surface 623 of the piston head 62. These grooves direct the airflow entering the first recess 613 from the abutment surface 622 to the sidewall surface 623, where it is ejected toward the inner wall 31 of the preload pipe 30 and then flows forward of the piston 60. In effect, these second channels 625 constitute the energy dissipation structure of the pressure control mechanism, deflecting the airflow output from the first channel to reduce the energy of the ejected airflow and thereby suppress the generation of flames. Preferably, the angle between the direction of the airflow output from the second channel 625 and impacting the inner wall 31 of the preload pipe 30 and the axial direction of the piston 60 (i.e., the direction of the airflow flowing through the first channel) is between 20° and 90°. For example, the second channel 625 may be configured to radially extend from the center of the abutting surface 622 of the piston head 62 to the outer wall 623 thereof, thereby allowing the airflow to vertically impact the inner wall 31 of the preload pipe 30 .

[0045] Preferably, the piston seat 61 is made of a first plastic material, such as POM (polyoxymethylene resin), which not only ensures an interference fit with the preload pipe 30 to achieve good sealing, but also allows the barrier portion 618 of the pressure control mechanism to rupture when the air pressure is too high, thereby ensuring safety; the piston head 62 is made of a second plastic material with a harderness greater than that of the first plastic material, such as nylon with glass fiber, to ensure support for the preload ball 70 and energy transmission. Of course, the piston seat 61 and the piston head 62 can also be made of the same material that meets the performance requirements, and the present invention does not limit this. In addition, to further suppress the generation of flames, the material of the piston seat 61 and / or the piston head 62 can be selected to be a flame-retardant material, or can contain a flame retardant additive component.

[0046] It can be understood that the specific materials listed above are only illustrative and not restrictive. In fact, any suitable material can be selected for the piston seat 61 and the piston head 62 to ensure that the piston 60 has sufficient heat resistance and ablation resistance and a high melting point. In other words, the selected material enables the piston 60 to withstand the friction heat between the piston 60 and the pre-tightening pipe 30 and the high temperature of the gunpowder during operation, so that the contact surface between the piston 60 and the pre-tightening pipe 30 will not form air leakage caused by heat or ablation.

[0047] It is also preferred that the size of the piston seat 61 is set so that the piston seat 61 has a basically cylindrical shape, the diameter of the piston seat 61 is larger than the diameter of the inner wall 31 of the preload pipe 30 so that the piston seat 61 forms an interference fit with the preload pipe 30, and the ratio of the length and diameter of the piston seat 61 is greater than or equal to 0.8, more preferably greater than or equal to 1, so that when the piston 60 is forced to move in the opposite direction of the preload, there is sufficient contact area with the inner wall 31 of the preload pipe 30 to provide resistance through friction so that the piston 60 hardly retreats.

[0048] Second embodiment

[0049] It should be understood that the different embodiments of the piston 60 according to the present invention have similar overall structures. Therefore, in the description of other embodiments, the same points as the embodiments already described will not be repeated.

[0050] As shown in Figures 5A to 5D , the second embodiment differs from the first embodiment in that the piston head 62 includes a support portion 626 that protrudes rearward from the abutment surface 622 and abuts against the first recess 613 of the piston seat 61. More specifically, the support portion 626 extends completely into the first recess 613, closely abutting and supporting the inner wall of the first recess 613. The provision of the support portion 626 ensures a more stable assembly between the piston head 62 and the piston seat 61, thereby ensuring stable movement of the piston 60 in the preload pipe 30 and preventing the piston 60 from tipping over or jumping during movement.

[0051] In this structure, at least one second channel 625 defined by the piston head 62 is, for example, a groove opened along the edge of the piston head 62, which extends from the end face 627 of the support portion 626 facing the first channel outlet 617 to the side wall surface 623, so as to guide the airflow reaching the first recess 613 from the support portion 626 to the side wall surface 623 of the piston head 62 and spray it toward the inner wall 31 of the preload pipe 30, and then flow toward the front of the piston 60.

[0052] Third embodiment

[0053] As shown in Figures 6A to 6D , the third embodiment differs from the first embodiment in that the first channel of the pressure control mechanism of the piston 60 includes a first channel inlet 616 recessed forward from the bottom of the middle portion 615 of the third recess of the piston seat 61, a first channel outlet 617 recessed rearward from the bottom of the first recess 613 of the piston seat 61, and a connecting channel 619 connecting the first channel inlet 616 and the first channel outlet 617. Thus, the middle portion 615 of the third recess and the first recess 613 are connected via the first channel.

[0054] In addition, the pressure control mechanism also includes a barrier 63 disposed within the first channel. This barrier 63 can be positioned within the first channel inlet 616, as shown, or within the first channel outlet 617 or the connecting channel 619. This barrier 63 is made of plastic or metal and functions similarly to the barrier 618 in the first embodiment, forming a diaphragm-like structure within the piston seat 61 that ruptures at preset pressures and temperatures. More specifically, when the gas pressure behind the piston seat 61 (i.e., the gas pressure within the third recess) is less than a preset value, the barrier 63 seals the first channel, preventing forward airflow. When the gas pressure behind the piston seat 61 is greater than or equal to the preset value, the barrier 63 ruptures through a fragile region, such as a weakened portion or tear line, to open the first channel, allowing airflow behind the piston seat 61 to reach the first recess 613 via the first channel. The present invention does not impose any restrictions on the shape, material, or rupture method of the barrier 63.

[0055] Fourth embodiment

[0056] As shown in Figures 7A to 7D , in the fourth embodiment, the difference from the third embodiment is that the structure of the piston head 62 is similar to that of the second embodiment, that is, the piston head 62 includes a support portion 626 that protrudes rearward from the abutment surface 622 and abuts against the first recess 613 of the piston seat 61, and the groove forming the second channel 625 guides the airflow reaching the first recess 613 from the support portion 626 to the side wall surface 623 of the piston head 62. For details, please refer to the second embodiment and will not be repeated here.

[0057] Fifth embodiment

[0058] As shown in FIG. 8A to FIG. 8D , in the fifth embodiment, the difference from the fourth embodiment lies in the arrangement of the first channel, that is, the first channel and the second channel 625 are both arranged in the piston head 62 .

[0059] More specifically, in the piston seat 61, the first recess 613 connects the front surface 611 with the middle portion 615 of the third recess. The support portion 626 of the piston head 62 extends completely into the first recess 613 toward the middle portion 615, closely abutting and supporting the inner wall of the first recess 613. In this fifth embodiment, the first passage of the pressure control mechanism of the piston 60 is disposed in the support portion 626 of the piston head 62. More specifically, the support portion 626 defines a first passage connecting the third recess of the piston seat 61 and the approximate center of the abutment surface 622 of the piston head 62. This first passage includes an inlet section 628 and a connecting section 629 connecting the inlet section 628 and the approximate center of the abutment surface 622. The barrier 63 can be disposed in the inlet section 628, as shown, or in the connecting section 629.

[0060] When the gas pressure behind the piston seat 61 (i.e., the gas pressure within the third recess) is less than a preset value, the barrier 63 can close the first passage to prevent the forward flow of the gas. When the gas pressure behind the piston seat 61 is greater than or equal to the preset value, the barrier 63 can rupture through a fragile area such as a weakened portion or tear line provided thereon to open the first passage, thereby directing the gas flow behind the piston seat 61 through the first passage to the approximate center of the abutment surface 622. It will be understood that the first passage can also be constructed in a manner similar to the first embodiment, i.e., the barrier 63 can be replaced by a barrier portion integrally formed in the piston head 62 to reduce the number of parts.

[0061] In addition, at least one second channel 625 defined by the piston head 62 is connected to the first channel at the end of the connecting section 629, and guides the airflow reaching the position of the abutment surface 622 from the approximate center position of the abutment surface 622 to the side wall surface 623 of the piston head 62 and sprays toward the inner wall 31 of the preload pipe 30, and then flows toward the front of the piston 60.

[0062] From the above detailed descriptions of the non-exhaustive embodiments, it can be seen that the piston 60 according to the present invention has a simple overall structure, a small number of parts, and a simple and reliable assembly process, so the production, process, and quality costs are low. When the pre-tightening is in effect, the piston 60 has excellent sealing properties to ensure gas sealing and energy transfer, while taking into account the response rate of power transmission and reducing hysteresis. When the pre-tightening device reaches the extreme working condition, in order to ensure the safety of the pre-tightening device and avoid the pre-tightening pipe 30 from bursting, the piston can release the high-temperature and high-pressure airflow in the pre-tightening pipe 30, and at the same time can effectively prevent open flames, high-energy particles, etc. from damaging the vehicle interior and harming the occupants.

[0063] It should be noted that the present invention (e.g., the inventive concept, etc.) has been described in the specification of this patent document and / or illustrated in the drawings based on exemplary embodiments; the embodiments of the present invention are presented only by way of example and are not intended to limit the scope of the invention. The structure and / or arrangement of the elements of the inventive concept embodied in the present invention as described in the specification and / or illustrated in the drawings is merely illustrative. Although exemplary embodiments of the present invention have been described in detail in this patent document, it is readily understood by those skilled in the art that equivalents, modifications, variations, etc. of the subject matter of the exemplary embodiments and alternative embodiments are possible and are considered to be within the scope of the present invention; all such subject matters (e.g., modifications, variations, embodiments, combinations, equivalents, etc.) are intended to be included within the scope of the present invention. It should also be noted that various other modifications, changes, substitutions, equivalents, alterations, omissions, etc. may be made in the configuration and / or arrangement of the exemplary embodiments (e.g., in terms of concept, design, structure, device, form, assembly, construction, means, function, system, process / method, step, order of process / method steps, operation, operating conditions, performance, materials, composition, combination, etc.) without departing from the scope of the present invention; all of these subjects (e.g., modifications, changes, embodiments, combinations, equivalents, etc.) are intended to be included within the scope of the present invention. The scope of the present invention is not intended to be limited to the subject matter described in the specification and / or drawings of this patent document (e.g., details, structures, functions, materials, behaviors, steps, orders, systems, results, etc.). Considering that the claims of this patent document will be appropriately interpreted to cover the full scope of the subject matter of the present invention (e.g., including any and all such modifications, changes, embodiments, combinations, equivalents, etc.); it should be understood that the terminology used in this patent document is intended to provide a description of the subject matter of the exemplary embodiments and is not intended to be used as a limitation on the scope of the present invention.

[0064] It should also be noted that, depending on the exemplary embodiments, the present invention may include conventional technologies (such as those implemented and / or integrated in the exemplary embodiments, modifications, variations, combinations, equivalents), or may include any other applicable technologies (present and / or future) that have the ability to perform the functions and processes / operations described in the specification and / or illustrated in the figures. All such technologies (such as those implemented in embodiments, modifications, variations, combinations, equivalents, etc.) are considered to be within the scope of the present invention of this patent document.

Claims

1. A piston (60) for a pre-tensioning seat belt, characterized in that: include: A piston seat (61), the piston seat (61) comprising a front surface (611) and a first recessed portion (613) recessed from the front surface (611); and A piston head (62), the piston head (62) being assembled to the front side of the piston seat (61) and comprising an abutting surface (622) abutting against the front surface (611), and the front side of the piston head (62) being provided with a second recess (621) suitable for supporting a transmission member; The piston (60) is provided with a pressure control mechanism, and the pressure control mechanism is configured to: block the airflow from flowing forward when the gas pressure on the rear side of the piston seat (61) is less than a preset value; and form an airflow channel when the gas pressure on the rear side of the piston seat (61) is greater than or equal to the preset value, and the airflow channel is suitable for deflecting the airflow and allowing the airflow to flow toward the front of the piston (60).

2. The piston (60) according to claim 1, characterized in that The piston seat (61) comprises at least one assembly portion (612) protruding from the front surface (611), and the piston head (62) comprises an assembly groove (624) that is snap-fitted with the at least one assembly portion (612).

3. The piston (60) according to claim 1, characterized in that A third recess is provided on the rear side of the piston seat (61), and the third recess includes a middle portion (615) and an edge portion (614) located outside the middle portion (615), wherein the middle portion (615) defines an assembly surface (6151) suitable for fitting an assembly tool, and the edge portion (614) is recessed from the edge of the assembly surface (6151) to form an annular edge (6141) suitable for radially outward deformation.

4. The piston (60) according to claim 3, characterized in that The assembly surface (6151) is an arc-shaped surface.

5. The piston (60) according to claim 3, characterized in that The pressure control mechanism comprises: a first channel inlet (616) recessed from the bottom of the middle portion (615); A first channel outlet (617) recessed from the bottom of the first recess (613); and A barrier portion (618) is located between the first channel inlet (616) and the first channel outlet (617), wherein the barrier portion (618) is configured to rupture when the gas pressure in the third recess is greater than or equal to the preset value to connect the first channel inlet (616) and the first channel outlet (617).

6. The piston (60) according to claim 3, characterized in that The pressure control mechanism comprises: a first passage connecting the middle portion (615) and the first recess (613); and A barrier (63) is arranged in the first channel, wherein the barrier (63) is configured to close the first channel when the gas pressure in the third recess is less than the preset value, and to rupture to open the first channel when the gas pressure in the third recess is greater than or equal to the preset value.

7. The piston (60) according to claim 5 or 6, characterized in that The pressure control mechanism also includes at least one second channel (625) defined by the piston head (62), and the at least one second channel (625) is configured to guide the air flow in the first recess (613) from the abutment surface (622) to the side wall surface (623) of the piston head (62).

8. The piston (60) according to claim 5 or 6, characterized in that The piston head (62) includes a support portion (626) protruding from the abutment surface (622) and abutting against the first recess (613), and the pressure control mechanism also includes at least one second channel (625) defined by the piston head (62), and the at least one second channel (625) is configured to guide the air flow in the first recess (613) from the support portion (626) to the side wall surface (623) of the piston head (62).

9. The piston (60) according to claim 3, characterized in that The first recess (613) communicates the front surface (611) with the middle portion (615), and the piston head (62) includes a support portion (626) protruding from the abutment surface (622) and abutting against the inner wall of the first recess (613), wherein the pressure control mechanism includes: A first channel defined by the support portion (626), the first channel being configured to The third recess is closed when the gas pressure in the third recess is less than the preset value, and is opened when the gas pressure in the third recess is greater than or equal to the preset value to guide the gas flow from the third recess to the position of the abutment surface (622); and At least one second channel (625) is configured to communicate with the first channel and guide the air flow from the position of the abutment surface (622) to the side wall surface (623) of the piston head (62).

10. The piston (60) according to claim 1, characterized in that The pressure control mechanism is configured so that the angle between the direction of the air flow output from the air flow channel and the axial direction of the piston (60) is between 20° and 90°.

11. The piston (60) according to claim 1, characterized in that The piston seat (61) is made of a first plastic material, and the piston head (62) is made of a second plastic material having a harderness than the first plastic material.

12. A seat belt retractor, characterized in that: include: Bracket (10); a reel assembly (20) rotatably mounted to the bracket (10), the reel assembly (20) comprising a reel (21) suitable for winding a webbing and a gear (22) fixedly connected to the reel (21); a pre-tightening pipe (30) assembled to the bracket (10); a gas generator (50) assembled into the preload pipe (30); and At least one piston (60) according to any one of claims 1 to 11 and at least one transmission member are arranged in the preload pipe (30), the piston (60) is arranged between the gas generator (50) and the transmission member, and the piston seat (61) is interference-fitted with the inner wall (31) of the preload pipe (30), The seat belt retractor is configured to generate an airflow when the gas generator (50) is ignited to push the piston (60) and the transmission member to move in the preload pipe (30), so that the transmission member interacts with the gear (22) and drives the reel (21) to rotate.

13. A pre-tensioned safety belt, characterized in that: The invention comprises a seat belt retractor according to claim 12.

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