Pre-tensioning device for seat belt retractor, and seat belt retractor

Abstract

A pre-tensioning device for a seat belt retractor, comprising: a tube assembly (3), wherein a set of mass bodies (3.4) are accommodated in a tube body (3.1) of the tube assembly; a gas generator (3.2); and a driving wheel (2.2) coupled to a reeling shaft. The tube body is provided with an extension portion (3.1.3) on an outlet side, and the extension portion surrounds the driving wheel and is open towards the driving wheel, so that the driving wheel can be driven by the mass bodies to rotate in a first rotating direction, and thus the reeling shaft can be driven by the driving wheel to rotate in the retracting direction of webbing. The tube body is provided with a clearance portion (3.1.4), the clearance portion forms a section of a guide path of the extension portion, and the clearance portion is designed to allow passage of the mass bodies when the driving wheel applies a pressure load to the clearance portion by means of the mass body located in an outlet area, so that the mass bodies can be engaged or disengaged with the driving wheel. Also provided are a seat belt retractor and a seat belt device. According to the pre-tensioning device, the operation reliability can be improved, and the situation that the mass bodies and the driving wheel are stuck during secondary engagement is avoided, avoiding the operation failure caused thereby.

Description

Pretensioner for seat belt retractor and seat belt retractor Technical Field

[0001] The present application relates to the field of safety technology, in particular to the field of vehicle safety technology, and more specifically to a pretensioning device for a seat belt retractor and a seat belt retractor comprising such a pretensioning device. Background Art

[0002] In modern vehicles, seatbelts are a crucial component of the vehicle's occupant restraint system. Especially in traffic accidents, seatbelts protect occupants, preventing or minimizing injury. With the increasing number of vehicles on the road, vehicle users are increasingly demanding the safety performance of seatbelts.

[0003] In conventional seatbelt systems, before a collision, there's a gap between the webbing and the occupant's body, potentially preventing the webbing from effectively fitting the occupant's body. In the event of a collision, this gap delays the belt's effective protection, reducing its effectiveness.

[0004] Patent document DE19512660A1 discloses a seatbelt device comprising a pretensioner comprising a number of masses. In the event of a collision, a gas generator is activated, and the gas generated by the gas generator drives the masses, which in turn drive a drive wheel coupled to a reel, causing the reel to rotate in the direction of webbing retraction, thereby achieving the pretensioning function of the seatbelt device.

[0005] When the seatbelt retractor's pretensioning function is activated, the force exerted by the occupant on the webbing can continue to increase after the webbing is pretensioned. At a certain point, this force exceeds the pretensioning force, causing the reel to rotate in the webbing extension direction, opposite to the webbing retraction direction. Under predetermined conditions, the seatbelt retractor's primary locking function can be triggered, preventing further webbing extension. If the seatbelt retractor has a force-limiting function, the force-limiting device activates when the force on the webbing exceeds a predetermined threshold, preventing the webbing from exerting excessive restraint force on the occupant's body and causing secondary injury. Summary of the Invention

[0006] During research and development, the inventors of the present application discovered that prior art seatbelt retractors with pretensioners may experience operational malfunctions and identified potential causes of these malfunctions. When the seatbelt assembly is worn by a vehicle occupant, the pretensioner's drive wheel may have an uncertain angular position due to various factors, including, but not limited to, varying occupant body types, varying seatbelt donning procedures, and manufacturing tolerances. Furthermore, due to collision energy, occupant body types, manufacturing tolerances, or other factors, the pretensioner may have varying pretension strokes upon activation. This uncertain angular position and pretension stroke of the drive wheel may result in the mass, which was about to disengage or had already disengaged from the drive wheel at the end of the pretensioning phase, being re-engaged by the drive wheel's teeth (also referred to as "secondary engagement") and subsequently driven into the tubular body by the drive wheel during secondary engagement. During this secondary engagement, the force exerted by the drive wheel on the mass fluctuates depending on the relative positions of the drive wheel and mass. In unfavorable circumstances, this force can jam or even completely block the drive wheel, preventing the spool coupled to the drive wheel from rotating normally in the webbing withdrawal direction and causing the seatbelt retractor to malfunction. If the seatbelt retractor has a force-limiting function, this function can be adversely affected by the jammed drive wheel, and the force-limiting function may even be completely lost.

[0007] The object of the present invention is to provide a pretensioning device for a seat belt retractor, a seat belt retractor comprising such a pretensioning device, and a seat belt device comprising such a seat belt retractor, wherein the pretensioning device, the seat belt retractor, and the seat belt device have improved operational reliability and avoid jamming of the mass body with the drive wheel and the resulting operational malfunctions when a secondary engagement occurs.

[0008] A first aspect of the present invention proposes a pretensioning device for a seat belt retractor, the pretensioning device comprising:

[0009] a tube assembly having a tube body in which a set of masses are housed;

[0010] a gas generator capable of generating pressurized gas when activated to drive the set of masses housed in the tube;

[0011] a drive wheel configured to be coupled to a reel of the seat belt retractor for winding the webbing;

[0012] The tube body has an extension portion on the outlet side, the extension portion surrounds the drive wheel and is open toward the drive wheel, so that when the gas generator is activated, the mass body that enters the extension portion from the tube body can engage with the drive wheel, so that the drive wheel can be driven to rotate in a first rotation direction by the mass body, and thereby the reel can be driven to rotate by the drive wheel in a webbing reeling direction;

[0013] In which, the tube body has an avoidance portion in the extension portion in an exit area where the mass body disengages from the drive wheel, and the avoidance portion forms a section of the guide path of the extension portion. The avoidance portion is designed so that when the drive wheel rotates in a second rotational direction opposite to the first rotational direction immediately after rotating in the first rotational direction, and when the drive wheel applies a pressure load to the avoidance portion through a mass body located in the exit area, the avoidance portion can avoid the mass body so that the mass body can enter into engagement with the drive wheel or can disengage from the drive wheel.

[0014] In the case of such a pre-tensioning device, when secondary engagement occurs, when the unfavorable angle of the drive wheel relative to the mass body may cause the drive wheel to be stuck by the mass body as in the prior art, the avoidance portion deforms under the pressure load of the mass body, so that the mass body can be smoothly placed into engagement with the drive wheel by the teeth of the drive wheel, or the mass body can be disengaged from the drive wheel, for example, enter a storage channel for the mass body, thereby at least substantially eliminating the working failure caused by the drive wheel being stuck by the mass body when secondary engagement occurs.

[0015] In some embodiments, the material of the escape portion may have a yield strength lower than that of the material of the extension portion.

[0016] In some embodiments, the extension portion of the tube body may be made of steel.

[0017] In some embodiments, the tube body may be made of steel.

[0018] In some embodiments, the avoidance portion may be at least partially made of a light metal material such as aluminum, magnesium, an aluminum alloy, a magnesium alloy and / or a plastic material.

[0019] In some embodiments, the avoidance portion can be made entirely of plastic material. As a supplement, a reinforcing material such as carbon fiber or glass fiber can be added to the matrix of the plastic material.

[0020] In some embodiments, the avoidance portion may be an injection molded component.

[0021] In some embodiments, the relief portion may be formed in one piece. Alternatively, the relief portion may be formed in multiple pieces.

[0022] In some embodiments, the relief portion may be mounted in the extension portion in a press-fit manner.

[0023] In some embodiments, the extension portion may have an opening, and the avoidance portion is installed in the opening.

[0024] In some embodiments, the avoidance portion can be installed in the opening in a press-fit manner. As an alternative or supplement, the avoidance portion can be fixed in the opening by fasteners such as screws, and / or fixed in the opening by welding or bonding.

[0025] In some embodiments, the opening may be an elongated opening extending in a longitudinal direction of the extension portion.

[0026] In some embodiments, the opening may be a square hole.

[0027] In some embodiments, the avoidance portion may include a base and a guide surface connected to the base, wherein the base is received in the opening.

[0028] In some embodiments, the guide surface may overlap with an opening edge region of the extension portion that defines the opening.

[0029] In some embodiments, the guide surface may have at least one of the following features:

[0030] - extends arcuately in cross section;

[0031] - in cross section, extends beyond the base on both sides;

[0032] - extends straight in a central longitudinal section;

[0033] - in a central longitudinal section, extends beyond the base on both sides;

[0034] - symmetrically constructed about a central longitudinal section;

[0035] - the edge on the inlet side has a transition bevel to the extension;

[0036] The edge on the outlet side has a step up to the extension.

[0037] In some embodiments, the base may have a plurality of interference ribs on two opposite longitudinal sides, respectively, and the interference ribs are pressed by the edge region of the opening, so that the base is received in the opening in a press-fit manner.

[0038] In some embodiments, the gas generator may be mounted on an end of the tube facing away from the extension portion.

[0039] In some embodiments, a piston assembly may be provided in the tube body for pushing the group of mass bodies when the gas generator is activated.

[0040] In some embodiments, a coupler may be provided in the tube body before the group of mass bodies, the coupler being configured to retain the group of mass bodies in the tube body when the gas generator is not activated, and to enter the extension portion and engage with the drive wheel when the gas generator is activated, so that the mass bodies entering the extension portion following the coupler have a certain angular position with the drive wheel.

[0041] In some embodiments, the mass body may be made of a metal material, in particular, steel.

[0042] In some embodiments, the mass body may be a sphere, an ellipsoid, or a roller.

[0043] In some embodiments, the set of masses are identically constructed.

[0044] In some embodiments, the pre-tightening device may include a guide for guiding the mass body away from the drive wheel in an exit region where the mass body is disengaged from the drive wheel.

[0045] In some embodiments, the relief portion may be surface treated so that the surface of the relief portion forming the guide path section has a reduced surface roughness. Alternatively or additionally, the relief portion may have a friction reducing coating, such as a Teflon coating or a molybdenum disulfide coating.

[0046] A second aspect of the present invention relates to a seat belt retractor, which includes a frame and a reel for winding a webbing, wherein the reel is rotatably supported in the frame, wherein the seat belt retractor also includes a pretensioning device for the seat belt retractor according to any embodiment of the present invention.

[0047] In some embodiments, a force limiting device may be integrated into the reel.

[0048] In some embodiments, the reel may include a reel body and a shaft head rotatably supported on one end of the reel body, and a force limiting rod, which is torque-proof connected to the reel body at one end and torque-proof connected to the shaft head at the other end.

[0049] In some embodiments, the drive wheel may be disposed coaxially with the reel.

[0050] In some embodiments, the drive wheel and the reel may be connected to each other in a rotationally fixed manner.

[0051] In some embodiments, the seat belt retractor may include a cover plate fixed to one side plate of the frame, the drive wheel being rotationally fixedly mounted between the cover plate and the side plate to an end section of the spool extending from the side plate.

[0052] In some embodiments, the seatbelt retractor may have a storage channel, wherein when the gas generator is activated, the mass body disengaged from the drive wheel can enter the storage channel, and the storage channel is jointly defined by the cover plate and the side plate.

[0053] In some embodiments, the seat belt retractor may be configured for use in a vehicle, in particular a land vehicle, such as a motor vehicle, in particular a passenger car, which may be driven by an internal combustion engine, a hybrid drive, or a purely electric drive.

[0054] In some embodiments, the seatbelt retractor may be configured to be mounted to a vehicle body or a vehicle seat.

[0055] Other aspects of the present invention may relate to a seat belt device including the seat belt retractor; a vehicle seat provided with the seat belt device; and a vehicle provided with the seat belt device or the vehicle seat.

[0056] In this document, a "torsionally rigid connection" may mean that the two connected components are essentially unable to rotate relative to each other, including but not limited to the following examples: 1) The two components are integrally formed and can therefore rotate together. 2) The two components can rotate together via a connecting structure, such as the two components being connected by a spline, or by a non-circular hole and a shaft with a non-circular cross-section. For example, the two components can be fixed to each other, or the two components can be unable to rotate relative to each other about an axis of rotation but can move relative to each other along the axis of rotation. 3) The two components are fixed to each other via a material-locked connection. For example, the two components are welded or adhesively bonded to each other. Combinations of various connection techniques are also possible.

[0057] The technical features mentioned above, the technical features described below, and the technical features shown individually in the accompanying drawings may be combined arbitrarily, as long as the combined technical features do not conflict with each other. All possible feature combinations are technical contents explicitly described in this document. Any of the multiple sub-features included in the same statement can be applied independently and does not necessarily have to be applied in conjunction with the other sub-features. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The present invention will be described in more detail below with reference to the accompanying drawings by means of exemplary embodiments. The accompanying drawings are briefly described as follows:

[0059] FIG. 1 is an exploded perspective view of a seat belt retractor according to an embodiment of the present invention.

[0060] FIG. 2 is a perspective view of a tube assembly of the seat belt retractor of FIG. 1 .

[0061] FIG. 3 is a partially cut-away view of the tube assembly of FIG. 2 .

[0062] 4A to 4C are perspective views, cross-sectional views, and central longitudinal sectional views of an escape portion according to an embodiment of the present invention.

[0063] FIG. 5 is an exploded perspective view of a spool and a drive wheel of the seat belt retractor of FIG. 1 .

[0064] 6 is a perspective view of an embodiment of a clutch for a pretensioning device.

[0065] FIG. 7 is a perspective view of an end cap of the seat belt retractor of FIG. 1 .

[0066] 8 to 11 are partially cutaway front views of the seat belt retractor of FIG. 1 , wherein the pretensioning device is in different states. DETAILED DESCRIPTION

[0067] A plurality of exemplary embodiments will now be described more fully with reference to the accompanying drawings. It should be appreciated that, for ease of illustration and understanding, elements that are not essential for understanding the present invention may be omitted in the accompanying drawings. In the accompanying drawings, the same reference numerals may represent the same components or components with the same function. Many specific details, such as examples of specific components, equipment, and methods, are described below to provide a thorough understanding of the embodiments of the present disclosure. It will be apparent to those skilled in the art that all of these specific details do not necessarily need to be adopted. The exemplary embodiments should not be construed as restrictive.

[0068] FIG1 is an exploded perspective view of a seat belt retractor 100 according to an exemplary embodiment of the present invention. The seat belt retractor 100 includes a frame 1. The frame 1 is typically configured as a U-shaped frame, which may have two side panels 1.1 and 1.2. The seat belt retractor 100 can be mounted to a motor vehicle via the frame 1, for example, to the body of the motor vehicle or the backrest of a vehicle seat. A reel 2 is rotatably supported in the frame 1. When the reel 2 rotates in a webbing reeling direction, the webbing of a seat belt device (not shown) can be wound onto the reel 2. When the reel 2 rotates in a webbing withdrawal direction, which is opposite to the webbing reeling direction, the webbing can be unwound from the reel 2. The reel 2 can be received in holes in the two side panels 1.1 and 1.2 of the U-shaped frame 1. For example, the spool 2 can be rotatably supported in a hole in the side plate 1.1. Furthermore, a toothed ring can be formed in the hole in the side plate 1.2. When engaged with the toothed ring, pawls or teeth (not shown) of the primary locking device can lock the spool 2. An end cap (not shown) can be provided axially adjacent to the side wall 1.2, and the primary locking device can be accommodated in the end cap. The spool 2 can be constructed as a single piece or as a multi-piece structure. Typically, when the seat belt retractor 100 has a force limiting function, the spool 2 is constructed as a multi-piece structure.

[0069] Please refer to Figure 5. In the embodiment shown in Figure 5, the seat belt retractor 100 has a force limiting function. To this end, a force limiting device is integrated into the reel 2. The reel 2 may include a reel body 2.1, which may be constructed as a hollow component, and a shaft head 2.4 is rotatably supported in the cavity of the reel body 2.1 at an open end of the reel body 2.1. The force limiting device includes a force limiting rod 2.3, which is accommodated in the cavity of the reel body 2.1 and is torsionally connected to the reel body 2.1 at one end and torsionally connected to the shaft head 2.4 at the other end. As can be seen in Figure 5, the force limiting rod 2.3 has splines on both ends, and the shaft head 2.4 also has splines in the hollow cylindrical part extending from the disc body. Similarly, the reel body 2.1 has splines that are not shown. The force limiting lever 2.3 can fail when a predetermined torsional load is exceeded, so that only a predetermined torsional load can be transmitted between the reel body 2.1 and the shaft head 2.4 by means of the force limiting lever 2.3. Force limiting functions for seat belt retractors are known in various forms in the prior art.

[0070] The seatbelt retractor 100 includes a pretensioning device 10. In an exemplary application scenario, a motor vehicle is equipped with the seatbelt retractor 100. In the event of a collision, the pretensioning device 10 can be activated, thereby pretensioning a webbing (not shown), eliminating gaps between the webbing and the occupant's body, and providing improved safety protection for the vehicle occupants. The pretensioning device 10 can include a drive wheel 2.2. The drive wheel 2.2 is configured as a ball gear having transmission grooves 2.2.1 distributed around its circumference. The transmission grooves 2.2.1 are separated from each other by ribs 2.2.2 or teeth. A mass body 3.4 configured as a sphere can engage with the drive wheel 2.2 in the transmission grooves 2.2.1. When a metal sphere is used as the mass body 3.4, the transmission groove 2.2.1 can also be referred to as a "ball socket." The drive wheel 2.2 is configured to couple with the reel 2. In the embodiment shown, the drive wheel 2.2 is arranged coaxially with the reel body 2.1 of the reel 2 and is mounted in a rotationally fixed manner on an end section 2.5 of the reel body 2.1 facing away from the spindle head 2.4.

[0071] The preload device 10 also includes a tube assembly 3, which is fixedly connected to the frame 1. Figure 2 is a perspective view of the tube assembly 3, and Figure 3 is a partially cutaway view of the tube assembly 3. The tube assembly 3 includes a tube body 3.1. The tube body 3.1 may include a main portion 3.1.1 having a complete peripheral wall and an extension portion 3.1.3 having an incomplete peripheral wall, wherein the extension portion 3.1.3 surrounds the drive wheel 2.2 and is open toward the drive wheel 2.2. The tube body 3.1 defines a channel 3.1.2, along which each mass body 3.4 can move one after another. These mass bodies 3.4 can each be configured as a metal sphere, in particular a steel ball. In an alternative embodiment, an ellipsoid or a roller can also be used as the mass body. For the sake of simplicity, the mass bodies 3.4 housed in the tube body 3.1 of the tube assembly 3 are not depicted in Figure 3. A fixed gas generator 3.2 and a movable piston assembly 3.3 are mounted on one end of the tubular body 3.1.

[0072] For example, in the event of a vehicle collision, when the gas generator 3.2 is activated, the gas generator 3.2 generates pressurized gas that can push the piston assembly 3.3 and thereby push a set of masses 3.4 downstream of the piston assembly 3.3 and a coupler 3.5 in front of the set of masses 3.4. An exemplary embodiment of the coupler 3.5 will be described in more detail below with reference to FIG6. The mass 3.4 that enters the extension 3.1.3 from the tube 3.1 (more specifically, the main portion 3.1.1 of the tube 3.1) can then engage with the drive wheel 2.2, causing the drive wheel 2.2 to rotate in a first rotational direction (counterclockwise in FIG1 ), and thereby rotating the reel 2 in the webbing retraction direction, thereby achieving the pretensioning function of the seatbelt retractor 100.

[0073] Figure 6 is a perspective view of an exemplary embodiment of the coupler 3.5. The coupler itself is known in the prior art in various forms. The exemplary coupler 3.5 may include a coupler body 3.5.1 and a coupler bracket 3.5.2. The coupler 3.5 may be configured to retain the set of masses 3.4 in the tubular body 3.1 when the gas generator 3.2 is not activated. To this end, the coupler bracket may have a protrusion 33 and the tubular body 3.1 may have a mounting hole 3.1.5 in which the protrusion 33 may be retained. The coupler 3.5 may be configured to disengage from the mounting hole 3.1.5 under the push of the piston assembly 3.3 when the gas generator 3.2 is activated, and then enter the extension 3.1.3 to engage with the drive wheel 2.2. In this case, the mass body 3.4 following the clutch 3.5 has a certain angular position with the drive wheel 2.2, and can well enter into meshing with the drive wheel 2.2, avoiding working failures in unfavorable relative angular positions. The clutch body 3.5.1 has a first sphere 21 and a second sphere 22. The first sphere 21 is part of a complete sphere, and the complete sphere can be constructed in roughly the same way as a mass body 3.4 constructed as a metal sphere. The second sphere 22 is a complete sphere and can be constructed in roughly the same way as a mass body 3.4 constructed as a metal sphere. When the preload function is activated, the relative angular position of the clutch 3.5 and all the mass bodies 3.4 relative to the transmission groove 2.2.1 of the drive wheel 2.2 is adjusted by the specific contour of the first sphere 21 of the clutch body 3.5.1, so that the second sphere 22 of the clutch 3.5 and the subsequent mass bodies 3.4 can well enter into meshing with the drive wheel 2.2. In the absence of the clutch 3.5, the first mass body entering the extension portion 3.1.3 may be in an unfavorable angular position relative to the drive wheel 2.2. In this angular position, the first mass body directly hits a tooth of the drive wheel 2.2 and cannot enter a transmission groove 2.2.1 of the drive wheel 2.2 well.

[0074] In the extension 3.1.3 of the tubular body 3.1, in the exit area where the mass body 3.4 disengages from the drive wheel 2.2, the tubular body 3.1 may have a relief portion 3.1.4. The relief portion 3.1.4 forms a section of the guide path of the extension 3.1.3. In an exemplary embodiment of the relief portion 3.1.4, see Figures 2, 3, and 4A to 4C. The tubular body 3.1 may have an opening 11 in the extension 3.1.3, and the relief portion 3.1.4 may be installed in the opening 11. To illustrate the opening 11, the relief portion 3.1.4 installed in the opening 11 is not shown in Figure 2. The opening 11 may be an elongated opening extending in the longitudinal direction of the extension 3.1.3. The relief portion 3.1.4 may be configured as an integral injection-molded component that is installed in the opening 11 by press-fitting. The relief portion 3.1.4 may include a base 12 and a guide surface 13 connected to the base 12. The base 12 is received in the opening 11. For example, the base 12 may have a plurality of interference ribs 14 on each of the two opposing longitudinal sides, and these interference ribs 14 are squeezed by the edge region of the opening so that the base 12 is received in the opening 11 in a press-fit manner. The guide surface 13 overlaps the edge region of the opening of the extension 3.1.3 that defines the opening 11. As can be seen in the cross-sectional view shown in FIG4B , the guide surface 13 extends in an arcuate shape in the cross section, with the two opposing longitudinal edges of the guide surface 13 respectively extending beyond the base 12 and resting on the surface of the extension 3.1.3 adjacent to the opening 11. As can be seen in the central longitudinal cross-sectional view shown in FIG4C , the guide surface 13 extends essentially in a straight line, with the edge of the guide surface 13 on the inlet side having a transition slope 15 to the extension 3.1.3, and the edge of the guide surface 13 on the outlet side having a step 16 to the extension 3.1.3. The transition slope 15 can be advantageous to ensure that the mass 3.4 smoothly reaches the guide surface 13 of the relief portion 3.1.4 when it is pushed from the tubular body 3.1 by the piston assembly 3.3. The step 16 can be advantageous to prevent the mass 3.4 from unintentionally returning to the guide surface 13 after passing the relief portion 3.1.4. The material of the relief portion 3.1.4 can have a lower yield strength than the material of the extension portion 3.1.3. For example, the entire tubular body 3.1 can be made of steel, while the relief portion 3.1.4 can be made of plastic, or alternatively, of aluminum or magnesium.

[0075] The working principle of the pretensioning device according to an exemplary embodiment of the present invention will now be described with reference to Figures 8 to 11. Figures 8 to 11 are partially cutaway front views of the seatbelt retractor 100 of Figure 1, wherein the pretensioning device 10 is in different states.

[0076] In the state shown in FIG. 8 , the pre-tightening device 10 is not activated and a set of masses 3.4 is held in the main portion 3.1.1 of the tubular body 3.1 by the engager 3.5.

[0077] In the state shown in Figure 9, the pretensioning device 10 has been activated and the pretensioning process is about to end. At this point, the clutch 3.5 and two masses 3.4 are already in the storage channel 5.1. One mass 3.4 (hereinafter referred to as the "special mass") is in contact with the guide 4 and is about to disengage from one of the transmission grooves 2.2.1 of the drive wheel 2.2. During the transition from the state shown in Figure 8 to the state shown in Figure 9, the group of masses 3.4 and the clutch 3.5, driven by the piston assembly 3.3, drive the drive wheel 2.2, causing it to rotate in a first rotational direction (counterclockwise in Figures 8 and 9). Consequently, the reel 2 coupled to the drive wheel 2.2 rotates in the webbing retraction direction, pretensioning the webbing and eliminating any gaps between the webbing and the occupant's body.

[0078] In the state shown in FIG10 , immediately after the pre-tensioning process, the drive wheel 2.2 is about to rotate in a second rotational direction (clockwise in FIG10 ), which is opposite to the first rotational direction. At this time, the ribs 2.2.2 or teeth of the drive wheel 2.2 squeeze the special mass. The inventors of the present application have discovered that in the prior art, an unfavorable relative angular position of the special mass relative to the drive wheel 2.2 may cause the drive wheel 2.2 to become stuck or even completely blocked, causing the reel 2 coupled to the drive wheel 2.2 to rotate poorly in the webbing withdrawal direction or even be unable to rotate in the webbing withdrawal direction, which may lead to a malfunction of the seatbelt retractor. In the event of a vehicle collision, such a malfunction may be detrimental to the safety protection of the occupants.

[0079] Now, due to the measures of the present invention, when the special mass engages the drive wheel 2.2 for the second time, the teeth of the drive wheel 2.2 press the special mass toward the clearance 3.1.4, and the clearance 3.1.4 can avoid the special mass. Therefore, in one possibility, the special mass can smoothly enter into engagement with the corresponding transmission groove 2.2.1 of the drive wheel 2.2, as shown in FIG11 . At this point, the special mass has already crossed the clearance 3.1.4 in the opposite direction, that is, it has left the clearance 3.1.4 from the inlet edge or transition slope 15 in the direction from the outlet edge to the inlet edge of the clearance 3.1.4. In another possibility, the special mass can smoothly disengage the drive wheel 2.2 and enter the storage channel 5.1.

[0080] In summary, the avoidance portion 3.1.4 is designed so that when the drive wheel 2.2 rotates in the second rotational direction immediately after rotating in the first rotational direction, when the drive wheel 2.2 applies a pressure load to the avoidance portion 3.1.4 through a mass body 3.4 (special mass body) located in the outlet area, the avoidance portion 3.1.4 can be squeezed and deformed, avoiding the mass body 3.4, so that the mass body 3.4 can enter into engagement with the drive wheel 2.2 or can disengage from the drive wheel 2.2.

[0081] Advantageously, the relief portion 3.1.4 can be surface-treated so that the surface of the relief portion 3.1.4 forming the guide path section has a reduced surface roughness. The relief portion 3.1.4 can have a lower coefficient of friction than the extension portion 3.1.3. Alternatively or in addition, the relief portion 3.1.4 can have a friction-reducing coating, such as a Teflon coating or a molybdenum disulfide coating. On the one hand, the base material of the relief portion 3.1.4 can have a lower coefficient of friction than the extension portion 3.1.3, and a further reduction in the coefficient of friction can be achieved by the coating. Due to the smooth surface of the relief portion 3.1.4, the mass body 3.4 can more easily enter into engagement with the drive wheel 2.2 during secondary engagement, or can more easily disengage the drive wheel 2.2 and enter the storage channel 5.1.

[0082] The preload device 10 may further include a guide 4 for guiding the masses 3.4 away from the drive wheel 2.2 in the exit region where the masses 3.4 disengage from the drive wheel 2.2. When a mass 3.4 reaches the guide 4, the guide portion 4.1 of the guide 4 separates the mass 3.4 from the transmission groove 2.2.1 of the drive wheel 2.2 and transfers it to the connecting channel 4.2, thereby allowing the mass 3.4 to reliably enter the storage channel 5.1.

[0083] The seatbelt retractor 100 may further include a cover plate 5 fixed to the side plate 1.1 of the frame 1, wherein the drive wheel 2.2 is non-rotatably mounted to the end section 2.5 of the reel 2 extending from the side plate 1.1 between the cover plate 5 and the side plate 1.1. The storage channel 5.1 is jointly defined by the cover plate 5 and the side plate 1.1.

[0084] It should be noted that the terms used herein are for the purpose of describing specific aspects only and are not intended to limit the disclosure. As used herein, the singular forms "a" and "the one" shall include the plural forms unless the context clearly indicates otherwise. It will be understood that the terms "include" and "comprise" and other similar terms, when used in the application documents, specify the presence of the stated operations, elements and / or parts, and do not exclude the presence or addition of one or more other operations, elements, parts and / or combinations thereof. As used herein, the term "and / or" includes all arbitrary combinations of one or more related enumerated items. In the description of the drawings, similar reference numerals always represent similar elements.

[0085] The thickness of the elements in the accompanying drawings can be exaggerated for the sake of clarity. It will also be understood that if an element is referred to as being on, coupled to, or connected to another element, then the element can be formed directly on, coupled to, or connected to the other element, or one or more intervening elements can be present between them. On the contrary, if the expressions "directly on...", "directly coupled to...", and "directly connected to..." are used herein, then there is no intervening element. Other words used to illustrate the relationship between elements should be interpreted similarly, such as "between..." and "directly between...", "attached to," and "directly attached to," "adjacent to," and "directly adjacent to," etc.

[0086] Terms such as "top," "bottom," "above," "below," "upper," "below," etc., are used herein to describe the relationship of one element, layer, or region to another element, layer, or region as illustrated in the figures. It will be understood that these terms are intended to encompass orientations of the device in addition to the orientation depicted in the figures.

[0087] It will be understood that although the terms "first," "second," and the like may be used herein to describe different elements, these elements should not be limited by these terms. These terms are merely used to distinguish one element from another. Thus, a first element may be referred to as a second element without departing from the teachings of the present invention.

[0088] It is also contemplated that all exemplary embodiments disclosed herein may be arbitrarily combined with one another. Finally, it should be noted that the above embodiments are intended only to provide an understanding of the present invention and do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that modifications may be made to the above embodiments without departing from the scope of protection of the present invention.

Claims

1. A pretensioning device for a seat belt retractor, the pretensioning device comprising: A tube assembly (3), the tube assembly having a tube body (3.1) in which a set of mass bodies (3.4) is accommodated; A gas generator (3.2), the gas generator being capable of generating pressurized gas upon activation to drive the set of mass bodies accommodated in the tube body; and A drive wheel (2.2), the drive wheel being configured to be coupled to a reel (2) of the seat belt retractor for winding the webbing; Wherein, the tube body (3.1) has an extension (3.1.3) on the outlet side, the extension surrounding the drive wheel and being open towards the drive wheel, such that the mass bodies entering the extension from the tube body upon activation of the gas generator can engage with the drive wheel, and thus the drive wheel can be driven to rotate by the mass bodies in a first rotational direction, and thereby the reel can be driven to rotate by the drive wheel in the webbing winding direction; Characterized in that, the tube body (3.1) has a relief portion (3.1.4) in the extension (3.1.3) in the outlet region where the mass body (3.4) disengages from the drive wheel (2.2), the relief portion forming a section of the guiding path of the extension, the relief portion being designed such that when the drive wheel rotates in a second rotational direction opposite to the first rotational direction immediately after the rotation in the first rotational direction, in the case where the drive wheel applies a pressure load to the relief portion through a mass body in the outlet region, the relief portion can avoid the mass body, such that the mass body can enter into engagement with the drive wheel or can disengage from the drive wheel.

2. The pre-tensioning device for a seat belt retractor according to claim 1, characterized in that, The material of the relief portion (3.1.4) has a yield strength smaller than that of the material of the extension (3.1.3).

3. The pretensioning device for a seat belt retractor according to claim 1 or 2, characterized in that, The tube body (3.1) is made of steel, and the relief portion (3.1.4) is at least partially made of a light metal material and / or a plastic material.

4. The pretensioning device for a seat belt retractor according to any one of claims 1 to 3, characterized in that, The extension (3.1.3) has an opening (11), and the relief portion (3.1.4) is installed in the opening.

5. The pre-tensioning device for a seat belt retractor according to claim 4, characterized in that, The opening (11) is an elongated opening extending in the longitudinal direction of the extension (3.1.3).

6. The pretensioning device for a seat belt retractor according to claim 4 or 5, characterized in that, The relief portion (3.1.4) has at least one of the following features: - Is an injection molded part; - Is integrally formed; - Is installed in the opening in a press fit manner.

7. The pretensioning device for a seat belt retractor according to any one of claims 4 to 6, characterized in that, The relief portion (3.1.4) includes a base portion (12) and a guiding surface (13) connected to the base portion, the base portion being received in the opening (11), and the guiding surface overlapping with the opening edge region of the extension that defines the opening.

8. The pretensioning device for a seat belt retractor according to claim 7, characterized in that, The guiding surface (13) has at least one of the following features: - Extends arcuately in cross-section; - Extends beyond the base portion on both sides in cross-section; - Extends linearly in the central longitudinal section; - Extends beyond the base portion on both sides in the central longitudinal section; - Is symmetrically formed with respect to the central longitudinal section; - The edge on the inlet side has a transition inclined surface (15) to the extension; - The edge on the outlet side has a step (16) to the extension.

9. The pretensioning device for a seat belt retractor according to claim 7 or 8, characterized in that, The base (12) has a plurality of interference ribs (14) on two opposite longitudinal sides, respectively. The interference ribs are pressed by the edge area of the opening, so that the base is received in the opening in a press-fit manner.

10. The pretensioning device for a seat belt retractor according to any one of claims 1 to 9, characterized in that: The gas generator (3.2) is mounted on the end of the tube (3.1) facing away from the extension; and / or A piston assembly (3.3) is provided in the tube (3.1) for pushing the group of masses when the gas generator is activated; and / or A coupler (3.5) is provided in the tube (3.1) before the group of mass bodies, and the coupler is configured to hold the group of mass bodies in the tube when the gas generator is not activated, and to enter the extension portion and engage with the drive wheel when the gas generator is activated, so that the mass bodies that follow the coupler and enter the extension portion have a certain angular position with the drive wheel.

11. The pretensioning device for a seat belt retractor according to any one of claims 1 to 10, characterized in that, The mass body is a sphere, an ellipsoid or a roller made of metal material.

12. The pre-tensioning device for a seat belt retractor according to any one of claims 1 to 11, characterized in that, The prestressing device (10) comprises a guide (4) for guiding the mass body away from the drive wheel in an exit area where the mass body is disengaged from the drive wheel.

13. The pretensioning device for a seat belt retractor according to any one of claims 1 to 12, characterized in that, The relief (3.1.4) is surface treated such that the surface of the relief forming the guide path section has a reduced surface roughness; and / or the relief (3.1.4) has a friction-reducing coating.

14. The pretensioning device for a seat belt retractor according to any one of claims 1 to 13, characterized in that, The drive wheel and the winding shaft are arranged coaxially and are connected to each other in a rotationally fixed manner.

15. A seat belt retractor, comprising a frame (1) and a reel (2) for winding a webbing, the reel being rotatably supported in the frame, characterized in that, The seat belt retractor further comprises a pretensioning device for a seat belt retractor according to any one of claims 1 to 14.

16. The seat belt retractor according to claim 15, characterized in that, A force limiting device is integrated into the reel.

17. The seat belt retractor according to claim 16, wherein, The reel (2) comprises a reel body (2.1), an axle head (2.4) rotatably supported on one end of the reel body, and a force-limiting lever (2.3), wherein the force-limiting lever is connected to the reel body in a rotationally fixed manner at one end and to the axle head in a rotationally fixed manner at the other end.

18. The seat belt retractor according to any one of claims 15 to 17, characterized in that, The seat belt retractor comprises a cover plate (5) fixed to a side plate (1.1) of the frame, the drive wheel (2.2) being mounted in a rotationally fixed manner between the cover plate and the side plate on an end section (2.5) of the winding shaft protruding from the side plate.

19. The seat belt retractor according to claim 18, wherein, The seat belt retractor has a storage channel (5.1), wherein when the gas generator is activated, a mass body disengaged from the drive wheel can enter the storage channel, and the storage channel is jointly defined by the cover plate and the side plate.

20. The seat belt retractor according to any one of claims 15 to 19, characterized in that, The seat belt retractor is configured for use in a motor vehicle.

21. A seat belt device, which includes a webbing, characterized in that, The seat belt device comprises a seat belt retractor according to any one of claims 15 to 20.

Images