Patent Publication Number: US-2022234539-A1

Title: Belt reel and also belt retractor having a belt reel

Description:
TECHNICAL FIELD 
     The invention relates to a belt reel for a belt retractor, comprising a rotational axis and a reel body provided as a reel for a webbing and having a first axial circumferential circle. Moreover, the invention relates to a belt retractor comprising a belt reel. 
     BACKGROUND 
     Belt retractors comprising a belt reel are known and serve for providing a seatbelt for a vehicle occupant of an automotive vehicle. During normal operation, the vehicle occupant can freely withdraw the seatbelt from the belt reel against the action of a winding spring, and the belt reel winds up the seatbelt again, when the vehicle occupant unbuckles the seatbelt, for example. Depending on external parameters such as the deceleration of the vehicle or the rotational acceleration of the belt reel when webbing is withdrawn, the blocking mechanism by which the belt reel can be blocked within the frame is activated. 
     When the belt reel is blocked within the frame, no more seatbelt can be withdrawn from the belt reel, until a predefined load level is reached in the seatbelt; the belt reel does not rotate relative to the frame of the belt retractor, with the exception of minimum yielding which is due to the inherent elasticity of all components present in the flux of force. 
     In order to find out how a belt retractor comprising a belt reel behaves in the case of restraint such as in the case of crash, the belt reel and the belt retractor comprising the belt reel are subjected to various tests, for example to the “ECE-R16 sled test” or the “loop load test according to FMVSS 209”. 
     SUMMARY 
     It is the object of the invention to provide a belt reel and a belt retractor comprising a belt reel which have improved characteristics in the case of restraint and, thus, increase the safety. 
     For achieving the object, a belt reel for a belt retractor is provided including a rotational axis and a reel body which is arranged as a reel for a webbing and has a first axial circumferential circle. The reel body further includes a first radial constriction with a second axial circumferential circle that is arranged centrally on the reel body in the axial direction. The circumference of the second axial circumferential circle amounts to a maximum of 95% of the circumference of the first axial circumferential circle. 
     In accordance with the invention, an axial circumferential circle is a circle having a radius that corresponds to the maximum radial distance of all points of the reel body from the rotational axis at the corresponding axial portion of the reel body. That is to say, the axial circumferential circle forms an envelope from which no point of the reel body protrudes at the corresponding axial portion. 
     The reel body is the part of the belt reel around which the webbing is wrapped at least in portions and which thus comprises the winding area to which the webbing is adjacent on the reel body. 
     This configuration causes the radial constriction to form a peripheral groove on the radial outer face of the reel body. In the case of load, particularly in the case of restraint, the webbing can constrict to the smaller diameter of the peripheral groove. Said constriction effectuates a reduction of the acting lever, which results in a reduction of the forward displacement in the sled test according to ECE R16 and in a reduction of the webbing extension in the loop load test according to FMVSS 209, when the same load-limiting system is used. Hence, the belt reel exhibits improved characteristics in the case of restraint, thereby improving the safety of a vehicle occupant who is protected by a safety system in such belt reel. 
     It is of advantage when the second axial circumferential circle is arranged centrally on the reel body in the axial direction. In this way, the webbing constricts symmetrically toward the center in the axial direction, thereby allowing the path of forces inside the webbing to be improved. 
     In one embodiment, the circumference of the second axial circumferential circle amounts to 80% to 95%, preferably to 85% to 90%, of the circumference of the first axial circumferential circle. Accordingly, on the one hand, the constriction is sufficiently deep to significantly reduce the acting lever, and, on the other hand, it is so flat that the webbing is not excessively deformed so that the characteristics of the seatbelt are impaired in the case of restraint. 
     The same advantages are offered by an embodiment in which the constriction has a depth of from 1 mm to 3 mm, particularly when the belt reel is provided for webbing having a width of 48 mm. 
     According to one embodiment, the second axial circumferential circle is disposed concentrically to the rotational axis and/or the constriction is formed to be rotationally symmetrical to the rotational axis. Accordingly, the constriction exhibits the same characteristics in all angular positions of the belt reel, whereby the effect of the constriction is provided independently of the angular position of the belt reel and thus the safety is reliably improved. 
     According to another embodiment, the constriction in the axial direction has a width of from 10% to 100%, preferably of from 20% to 40%, of the axial length of the reel body. This configuration helps ensure that the webbing can constrict in a defined manner by being guided over a sufficiently large axial area in the constriction. 
     The constriction may have a concave profile, causing the webbing to be deformed in a way that promotes the path of forces inside the webbing in the case of restraint. 
     It is advantageous when the constriction is symmetrical, particularly mirror-symmetrical, to a plane, in particular to the axial central plane of the reel body, as in this way the webbing is symmetrically loaded in the axial direction during constriction and, thus, the characteristics improve in the case of restraint. 
     In another embodiment, between the constriction and adjacent axial portions, the reel body has respective axial transition portions in which the axial circumferential circle steadily changes in the axial direction from the first axial circumferential circle to the second axial circumferential circle. In particular, the axial transition portions are designed to be free of edges. In this way, local load peaks are prevented from forming in the webbing, thereby improving the characteristics in the case of restraint and, consequently, the safety. 
     In accordance with the invention, for achieving the afore-mentioned object also a belt retractor comprising a belt reel according to the invention offering the above-mentioned advantages is provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages and features will be evident from the following description and from the attached drawings, wherein: 
         FIG. 1  shows a schematic representation of a belt retractor according to the invention comprising a belt reel according to the invention, 
         FIG. 2  shows the belt reel of  FIG. 1  in a lateral view, 
         FIG. 3  shows the belt reel of  FIG. 1  in a sectional view across the plane A, and 
         FIG. 4  shows the belt reel of  FIG. 1  in a sectional view across the plane B. 
     
    
    
     DESCRIPTION 
       FIG. 1  illustrates a belt retractor  10  comprising a frame  12  and a belt reel  14  which is rotatably supported about the rotational axis R within the frame  12 . 
     The belt retractor  10  is part of a seatbelt system, in particular in a vehicle. 
     The belt reel  14  includes a reel body  16  as well as axial lateral portions  18 ,  19  disposed opposed to each other in the axial direction A which delimit the reel body  16  in the axial direction A. 
     In an alternative embodiment, the belt reel  14  may or may not have an axial lateral portion  18 ,  19 . 
     The reel body  16  has a circular-cylindrical basic shape and a winding area  20  which is formed by the radial outer face  22  of the reel body  16  and on which a webbing  24  of a seatbelt can be wound and unwound. 
     In the axial direction A, the reel body  16  includes a first axial portion  26 , a second axial portion  28  and a third axial portion  30 . 
     The second axial portion  28  that is disposed in the axial direction A between the first axial portion  26  and the third axial portion  30  includes a radial constriction  32 . 
     The radial constriction  32  is a radial recess extending in the circumferential direction U on the radial outer face  22  of the reel body  16  which forms the winding area  20 . 
     Accordingly, the radial constriction  32  is rotationally symmetrical to the rotational axis R. 
     Basically, in an alternative embodiment the constriction  32  may be designed substantially at will. In particular, the reel body  16  may have radial recesses and/or radial extensions in the axial portion of the constriction  32 . 
     The first axial portion  26  has a first axial circumferential circle  34  (see  FIG. 3 ) with a radius r 1  and the constriction  32  has a second axial circumferential circle  36  with a radius r 2  that is smaller than the radius r 1 . 
     Each of the centers of the first circumferential circle  34  and of the second circumferential circle  36  is located on the rotational axis R, thus causing the first circumferential circle  34  and the second circumferential circle  36  to be arranged concentrically to each other. 
     The third axial portion  30  has a third axial circumferential circle  38  which is designed analogously to the first circumferential circle  34 . I.e., the third circumferential circle has a radius r 1  and a center that is located on the rotational axis R. 
     Each of the first and third circumferential circles  34 ,  38  is the circumferential circle having the largest circumference of the first and, resp., third axial portions  26 ,  30 . 
     The second circumferential circle  36  is the circumferential circle having the smallest circumference of the second axial portion  28  and the constriction  32 . 
     In an alternative embodiment, each axial portion  26 ,  28 ,  30  as well as the constriction  32  may have an individual circumferential circle  34 ,  36 ,  38  which may differ from each other, particularly as to their radius and/or the position of their center relative to the rotational axis R. 
     In addition, or as an alternative, the circumference of the circumferential circle  34 ,  36 ,  38  may have any size in the corresponding axial portion  26 ,  28 ,  30  and in the constriction  32  relative to further circumferential circles in the corresponding axial portion  26 ,  28 ,  30  as well as in the constriction  32 . 
     Preferably, each of the radii of the first circumferential circle  34  and of the third circumferential circle  38  is larger than the radius r 2  of the second circumferential circle  36 . 
     The circumference of the second circumferential circle  36  amounts to 90% of the circumference of the first circumferential circle  34 . 
     In an alternative embodiment, the circumference of the second circumferential circle  36  may be from 80% to 95%, preferably from 85% to 90%, of the circumference of the first circumferential circle  34 . 
     Basically, the circumference of the second circumferential circle  36  is allowed to amount to a maximum of 95% of the circumference of the first circumferential circle  34  so that the constriction  32  has a sufficient depth t so that the webbing  24  can appropriately constrict to the smaller diameter, as will be described later. 
     The depth t corresponds to the difference of the first radius r 1  and the second radius r 2  and, in the shown embodiment, amounts to 2 mm. 
     In an alternative embodiment, the depth t of the constriction  32  may be between 1 mm and 3 mm. 
     The constriction  32  is provided, in the axial direction A, centrally on the reel body  16 , i.e., equally distanced from both axial ends of the reel body  16 . 
     Furthermore, the second circumferential circle  36  is located in the axial central plane  40   t  which, in  FIG. 2 , at the same time forms the sectional plane A-A. 
     Thus, the second circumferential circle  36  is arranged, in the axial direction A, centrally on the reel body  16  as well as centrally on the winding area  20 . 
     The constriction  32  is designed symmetrically to the axial central plane  40  and has a concave profile (see  FIG. 4 ). 
     The reel body  16  further includes axial transition portions  42 ,  43  which extend from the second circumferential circle  36  to the first axial portion  26  and, resp., the third axial portion  30  and which are designed so that the radii of the axial circumferential circles in said axial transition portions  42 ,  43  steadily increase from r 2  to r 1  in the axial direction A between the second circumferential circle  36  and the first circumferential circle  34  or, resp., the third circumferential circle  38 . 
     The axial transition portions  42 ,  43  are rounded and, thus, are free of edges so as to provide an advantageous transmission of the loads from the winding area  20  to the webbing  24  in the case of restraint. 
     Basically, the reel body  16  may have a profile of any course. 
     The constriction  32  has a width b in the axial direction A (see  FIG. 4 ) which amounts to 30% of the axial length L of the reel body  16 . 
     In the present embodiment, in which the belt reel  14  is provided for a webbing  24  having a width of 48 mm, the length L of the reel body  16  amounts to 50 mm and the width b of the constriction  32  amounts to 15 mm. 
     In an alternative embodiment, the width b of the constriction  32  may be between 10% and 100%, in particular between 20% and 40% of the axial length L of the reel body  16 . 
     This means particularly that, according to an alternative embodiment, the constriction  32  may extend over the entire axial length L of the reel body  16 . 
     Accordingly, the axial length L of the reel body  16  at the same time corresponds to the axial length of the winding area  20 . 
     The reel body  16  further includes mounting pockets  44  and an axial gap  46  dividing the reel body  16  which interrupt the winding area  20 . 
     In an alternative embodiment, the reel body  16  may have no or any number of geometrical elements such as pockets, gaps and/or projections. 
     In addition, or as an alternative, the reel body  16  may have any basic shape. 
     In particular, the reel body  16  may include, in the circumferential direction, a radial step to which one end of the webbing  24  is fastened so that, at the step, the webbing  24  merges tangentially into the second winding. 
     Moreover, the belt reel  14  includes a cavity  48  extending along the rotational axis R (see  FIG. 4 ) in which a rod-shaped or tubular load-limiting element that is part of a load limiter of the belt retractor  10  can be disposed. 
     The belt retractor  10  can basically include any load-limiting elements. This means that the belt reel  14  is compatible with the common load limiters and can be used, jointly with the latter, in a belt retractor  10 . 
     If the webbing  24  is loaded in the case of restraint, for example in the case of crash, the constriction  32  results in the webbing  24  being partially wound on the reel body  16  constricting at least partially to the smaller diameter of the second circumferential circle  36 . Said constricting causes the acting lever to decrease, in particular to the radius r 2 , and consequently the acting forces of the webbing  24  being reduced to the belt reel  14 . 
     This effect is additionally promoted by the afore-described geometrical design of the reel body  16  and the constriction  32 . 
     In this way, a belt reel  14  is provided which results in a reduction of the forward displacement in the sled test according to ECE R16 and in a reduction of the webbing extension in the loop load test according to FMVSS 209. 
     The belt reel thus exhibits improved characteristics in the case of restraint, thereby improving the safety of a vehicle occupant who is protected by a safety system in such belt reel. 
     The invention is not limited to the shown embodiment. In particular, individual features of one embodiment can be combined at will with features of other embodiments, particularly independently of the other features of the respective embodiments.