CN108238001A - Torsion bar for safety belt retractor, safety belt retractor and safety belt assembly - Google Patents

Abstract

The invention provides a torsion bar for a safety belt retractor, which is in a bar shape, wherein two end parts and the middle part of the torsion bar are respectively provided with a circumferential external tooth, at least one of two bar sections positioned at two sides of the circumferential external tooth at the middle part of the torsion bar is provided with a fracture inducing groove, and the fracture inducing grooves on the two torsion bars are respectively provided with a preset effective depth and an effective width, so that when the torsion bar rotates along with a mandrel, one of the two torsion bar sections is firstly fractured. The torsion bar is a degressive force limiting torsion bar, can realize secondary degressive force limiting when applied to the installation belt, has good universality, and can be suitable for different vehicle types only by processing the fracture induction groove. The invention also provides a safety belt retractor using the torsion bar and a safety belt assembly using the safety belt retractor.

Description

Torsion bar for seat belt retractor, seat belt retractor and seat belt assembly

This application requires a Chinese patent application submitted to the China Patent Office on December 26, 2016 with the application number 201611217783.4 and the title of the invention as "torque bar for seat belt retractor, seat belt retractor and seat belt assembly" priority, the entire contents of which are incorporated in this application by reference.

technical field

The invention relates to the technical field of seat belts, in particular to a torsion bar for a seat belt retractor. The present invention also relates to a seat belt retractor using the torsion bar, and a seat belt assembly using the above seat belt retractor.

Background technique

The seat belt is the basic safety protection device of the car. When the vehicle collides, it can avoid or reduce the dangers such as secondary collision between the user and the objects in the car or being directly thrown out of the car.

The traditional safety belt is an emergency locking safety belt, and its retractor is equipped with a locking mechanism. When the car collides, the locking mechanism can immediately stop the rotation of the reel, so that the webbing is no longer stretched out, so that the The occupant is secured in the car seat. However, due to the inertia of the occupant, the force exerted by the webbing on the occupant increases sharply at the moment of collision, which may cause the occupant to be injured by the seat belt.

In order to alleviate the impact of the seat belt on the occupant when the car collides, people have invented a force-limiting seat belt. The webbing reduces the impact of the webbing on the passenger's chest, thus protecting the safety of the occupants to the greatest extent. In order to further reduce the force of the webbing of the seat belt acting on the occupant's chest, so that the occupant can obtain better protection effect, a multi-stage decreasing force-limiting seat belt was invented.

The existing two-stage force-limiting seat belt adopts a two-stage torsion bar formed by axially butting two sections of torsion bars with different lengths to realize two-stage force limitation. The structure is simple, but it also has certain defects. The force limiting characteristic of the torsion bar is obtained by matching the length of the two torsion bars. When a new force limiting feature is required, if the total length of the torsion bar remains unchanged, there is no need to replace the retractor. At this time, the two torsion bars are both It needs to be replaced; if the total length of the torsion bar is changed, the retractor needs to be replaced. In this case, at least one section of the torsion bar needs to be replaced. Therefore, the torsion bar has poor versatility. For models with different force limiting characteristics, the retractor needs to be replaced at the same time Retractor and/or one or two sections of torsion bar, so the reusability rate of retractors and torsion bars of the same specification is extremely low, and it is necessary to design and process retractors and torsion bars of different specifications multiple times to meet different limit requirements. Resulting in increased development and manufacturing costs for seat belts.

Contents of the invention

In order to solve the above technical problems, the present invention provides a torsion bar for a safety belt. The present invention additionally provides a retractor and seat belt assembly using the torsion bar.

The invention provides a torsion bar for a seat belt retractor, the seat belt retractor includes a retractor frame, a reel and a torsion bar; the seat belt retractor frame includes two opposite side walls, The positions corresponding to the two side walls are respectively provided with circular holes with internal teeth; the reel includes a through hole arranged along the central axis and is used for winding the mandrel of the ribbon, and is detachably arranged on both sides of the mandrel. The two end caps at the end; the central position of the end cap is provided with a central concave hole or a through hole with internal teeth, which is used to fix the two ends of the torsion bar, and the end cap is provided with The internal teeth on the retractor frame match the external teeth, which are used to lock the reel; the middle position of the through hole at the central axis of the mandrel is provided with internal teeth; the torsion bar is rod-shaped, The through hole passing through the mandrel is provided with circumferential external teeth at both ends and in the middle, and the circumferential external teeth at both ends of the torsion bar are respectively connected with the said retractor. The inner teeth of the central concave hole or the through hole of the two end caps are matched, and the circumferential outer teeth of the middle part of the torsion bar are matched with the inner teeth of the middle position of the through hole at the central line of the mandrel. It is characterized in that at least one of the two rod sections located on both sides of the circumferential outer teeth in the middle of the torsion bar is provided with a fracture induction groove, and the fracture induction grooves on the two sections of the torsion bar are all provided with predetermined effective The depth and the effective width are such that when the torsion bar twists with the mandrel, one of the two torsion bar segments breaks first.

Preferably, the fracture induction groove is an annular groove along the circumferential direction of the torsion bar.

Preferably, the fracture induction groove is coaxial with the torsion bar.

Preferably, the fracture induction groove is an annular groove.

Preferably, the circular fracture induction groove is provided with predetermined groove depth and groove width.

Preferably, the number of the fracture induction groove is one.

Preferably, the circumferential outer teeth of the middle part of the torsion bar are all provided with avoidance missing teeth, and the position of avoiding missing teeth corresponds to the fixing groove on the mandrel passing through and fixing the end of the webbing.

Preferably, the torsion bar is formed by butting two sections of the torsion bar in the axial direction, and both ends of each section of the torsion bar are provided with circumferential external teeth, and the circumferential external teeth of the butt ends of the two sections of the torsion bar have a tooth profile Aligned and are provided with avoidance missing teeth at positions corresponding to the fixed slots on the mandrel passing through and fixing the ends of the webbing; the circumferential outer teeth at the butt joint ends of the two sections of torsion bars jointly constitute the middle part of the torsion bar. Circumferential outer teeth; the avoidance missing teeth on the circumferential outer teeth at the butt joint ends of the two sections of torsion bars together form the avoidance missing teeth on the circumferential outer teeth in the middle of the torsion bar.

Preferably, at least one of the diameter, material and effective length of the two sections of the torsion bar is different.

In addition, the present invention also provides a safety belt retractor using the torsion bar provided by the above technical solution.

At the same time, the present invention also provides a seat belt assembly using the above-mentioned seat belt retractor.

Compared with prior art, the present invention has the following advantages:

In the torsion bar used for the safety belt retractor provided by the present invention, at least one of the two bar sections on both sides of the circumferential outer teeth in the middle is provided with a fracture induction groove, and only the existing fracture induction groove needs to be adjusted New force-limiting characteristics can be obtained by adding a new effective width or/and effective depth or adding a new fracture induction groove. For models with different force-limiting characteristics, it is only necessary to design and process the induction groove of the torsion bar without replacing the retractor , and there is no need to change the diameter, length or material of the two sections of the torsion bar to meet the requirements. Therefore, the versatility of the retractor and the torsion bar of the same specification is also greatly increased, thereby also reducing the research and development and manufacturing costs of the safety belt.

Description of drawings

Fig. 1 is the axial sectional view of the reel of the present invention

Fig. 2 is a schematic diagram of a section of the torsion bar provided with a fracture induction groove in the two-section torsion bar of the present invention.

Fig. 3 is the structural representation of the embodiment of the retractor for safety belt of the present invention

Fig. 4 is an axial cross-sectional view of the reel comprising two torsion bar sections with different diameters and different effective lengths in the first embodiment of the present invention, and one section of the torsion bar has a fracture induction groove

Figure 5 is an axial sectional view of a reel using a torsion bar in a second embodiment of the present invention

Fig. 6 is an axial sectional view of a torsion bar in a third embodiment of the present invention

Figure 7 is a characteristic curve diagram of a seat belt retractor with two-stage decreasing force-limiting characteristics

Detailed ways

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described here, and those skilled in the art can make similar extensions without violating the connotation of the present invention, so the present invention is not limited by the specific implementations disclosed below.

first embodiment

In this embodiment, the torsion bar is rod-shaped, and the torsion bar is formed by butting two sections of the torsion bar in the axial direction, and one section of the torsion bar is provided with a circular fracture induction groove coaxial with the torsion bar along the circumferential direction . Please refer to Fig. 1, which is a schematic structural view of a reel using the torsion bar in this embodiment, wherein the torsion bar 1 is the torsion bar, as shown in Fig. 1, the torsion bar 1 is composed of a torsion bar 1a and The two ends of the torsion bar 1b are butted in the circumferential direction of the torsion bar, and the torsion bar 1a is provided with a ring-shaped fracture induction groove 1a-1 coaxial with the torsion bar along its circumferential direction. The depth of the fracture induction groove is D, the width is L. Referring to Fig. 2, this figure is a schematic structural view of the torsion bar 1a provided with the fracture induction groove 1a-1, and its two ends are provided with circumferential outer teeth 1a-2 and 1a-3 and circumferentially outward Tooth 1a-3 is provided with avoidance missing tooth 1a-3-1, and the position of this missing tooth corresponds to the fixing groove on the mandrel that passes through and fixes the end of the seat belt webbing; Both ends are also provided with circumferential external teeth 1b-2 and 1b-3, and the circumferential external teeth 1b-3 are provided with avoidance missing teeth 1b-3-1 (not shown), the position of the missing teeth is also Corresponds to the fixing slot on the mandrel that passes through and fixes the end of the seat belt webbing. The tooth shape of the peripheral external teeth 1a-3 and the avoidance missing teeth 1a-3-1 and the tooth shape of the circumferential external teeth 1b-3 and the avoidance missing teeth 1b- 3-1 (not shown) are aligned respectively. Referring to Fig. 1, when the torsion bar 1a and 1b are butted together to form a torsion bar 1, the end where the peripheral external teeth 1a-3 are located and the end surface of the end where the peripheral external teeth 1b-3 are located abut against each other connected, and the teeth of the peripheral outer teeth 1a-3 and the avoidance missing teeth 1a-3-1 and the teeth of the peripheral outer teeth 1b-3 and the avoidance missing teeth 1b-3-1 Aligned respectively, the peripheral external teeth 1a-3 and 1b-3 jointly constitute the middle peripheral external teeth 1-1 of the torsion bar 1, and the missing teeth 1a-3-1 and 1b-3-1 jointly Consists of a missing tooth 1-1-1 (not shown) corresponding to the position on the central circumferential outer tooth 1-1 and the fixing groove passing through and fixing the end of the seat belt webbing on the mandrel. The peripheral outer teeth 1a-2 and 1b-2 of the two ends of the torsion bar 1 are matched with the inner teeth of the central concave hole or the through hole of the two end caps on the retractor, and the torsion bar 1 The middle peripheral outer teeth 1-1 of the middle part are matched with the inner teeth of the through hole of the mandrel.

In order to better understand the torsion bar of this embodiment, the torsion bar of the present invention will be described in detail below in conjunction with the seat belt retractor to which the torsion bar is applied. It should be noted that in this embodiment, the description of other components of the seat belt retractor is mainly for better understanding of the torsion bar of this embodiment, and this description should not limit the protection scope of the claims of this application.

Referring to FIG. 3 , it is a structural diagram of a seat belt retractor of the present invention, and the seat belt retractor includes the torsion bar 1 , retractor frame 2 and reel 3 . The retractor frame 2 includes two opposite side walls: a first side wall 2-1 and a second side wall 2-2, where the first side wall 2-1 and the second side wall 2-2 correspond The positions are respectively provided with a first through hole 2-1a (not shown) and a second through hole 2-2a, and the first through hole 2-1a (not shown) and the second through hole 2-2a are both They are circular, and are provided with internal tooth segments 2-3 at the same position, and the internal tooth segments are used to cooperate with the external teeth on the spool 3 to lock the spool 3.

The safety belt retractor is also provided with other structures, which will not be repeated here.

Referring to FIG. 1 , the reel 3 includes a mandrel 3-1, and two end caps separately disposed on both ends of the mandrel 3-1: a left end cap 3-2a and a right end cap 3-2b.

The mandrel 3-1 is used for winding the safety belt webbing, and the mandrel 3-1 is provided with a through hole 3-3 along its central axis, and the inner wall of the through hole 3-3 is provided with internal teeth.

The mandrel mandrel 3-1 is also provided with an oblong fixing slot 3-4 for passing through and fixing the end of the webbing of the safety belt.

Referring to FIG. 3 , two force-limiting pins 3-5 protruding outward are respectively provided on the two end surfaces of the mandrel mandrel 3-1.

The mandrel 3-1 is also provided with a weight reduction groove 3-6 for weight reduction.

As shown in Figure 1, the end caps 3-2a and 3-2b are provided with a central concave hole with internal teeth at the center of the inner end surface facing the mandrel 3-1, and the left end cap 3-2a The central concave hole 3-2a-1 of and the central concave hole 3-2b-1 on the right end cover 3-2b. In this embodiment, the concave holes of the two end caps are arranged on the boss protruding from the side of the end surface where they are located. The corresponding end face of the mandrel is provided with a notch for accommodating the boss.

The end caps 3-2a and 3-2b are all provided with external teeth, as shown in Figure 1, the external teeth 3-2a-2 on the left end cap 3-2a and the external teeth on the right end cap 3-2b Teeth 3-2b-2, and they all cooperate with the inner tooth segments 2-3 on the side walls 2-1 and 2-2 of the retractor frame. When the safety belt is locked, the outer teeth 3-2a-2 and 3-2b-2 mesh with the inner tooth segment 2-3.

The positions of the end caps 3-2a and 3-2b corresponding to the force limiting pins 3-5 on the two end faces of the mandrel 3-1 on the end face side facing the mandrel 3-1 are respectively Pin holes are provided, as shown in Figure 3, the pin holes 3-2b-2 of the right side end cover 3-2b are arranged on the two ends of the mandrel 3-1 on both ends of the cover as shown in Figure 1 , the force limiting pin is inserted into the corresponding pin hole. The setting positions of the force limiting pin 3-5 at both ends of the mandrel can be different, so that it can be used for positioning when the end cover and the mandrel 3-1 are assembled, so as to prevent the wrong assembly of the left and right end covers. More importantly, the force limiting pin 3-5 can also bear the shearing force when the mandrel rotates, and be cut off when the shearing force reaches a threshold.

On the outer end surface side of the two end caps away from the core shaft 3 - 1 , a protruding shaft protruding outward is arranged along the center of the end surface. The right protruding shaft 3-2b-3 and the left protruding shaft 3-2a-3 are shown in Fig. 1 . Wherein, the left extension shaft 2-2a-3 is connected with the sensitive element, and the right extension shaft 2-2b-3 is provided with teeth on the outer periphery, and is connected with the coil spring.

The torsion bar 1 passes through the through hole 3-3 and the middle peripheral outer teeth 1-1 mesh with the inner teeth on the inner wall of the through hole 3-3, the torsion bar 1 The avoidance missing tooth 1-1-1 on the central peripheral outer tooth 1-1 is aligned with the fixing groove 3-4 on the core shaft 3-1. The left end cover 3-2a and the right end cover 2-2b respectively cover both ends of the mandrel 3-1 from the left and right sides, and the force limiting pins at the corresponding positions correspond to the pin holes. The two ends of the torsion bar 1 are respectively inserted into the central concave holes of the left and right end covers 3-2a and 3-2b, and the peripheral outer teeth 1a-2 and 1b-2 are respectively connected to the central concave holes. The holes 3-2a-1 and 3-2b-1 are engaged.

The reel 3 is integrally arranged in the retractor frame 2 , and the two end caps on the reel 3 are respectively arranged in the side wall through holes of the retractor frame 2 . In the free state, the spool 3 can be rotated and floated in the retractor frame 2, the outer teeth on the end cap do not contact the inner teeth on the retractor frame 2, and the spool 3 can rotate freely. Realize the winding and releasing of webbing. While in the locked state, the outer teeth on the two ends of the spool 3 are engaged with the inner teeth on the retractor frame, so the spool 3 cannot rotate.

In this embodiment, the end caps 3-2a and 3-2b are provided with central concave holes for fixing the torsion bar 1 when the length of the torsion bar 1 is not greater than the axial length of the seat belt retractor. The two ends of the torsion bar 1 are described. In another real-time mode, the length of the torsion bar 1 can also be greater than the axial length of the safety belt retractor, and at this time, a central channel is opened at the center position of the end covers 3-2a and 3-2b correspondingly. Holes for fixing the two ends of the torsion bar 1.

In this embodiment, the torsion bar 1 is set as two separate sections of torsion bar 1a and 1b, and the torsion bar 1a is provided with a fracture induction groove. In this case, different fracture induction grooves or different diameters or different materials or different effective lengths of the torsion bars 1a and 1b at both ends are used in combination, or the torsion bars 1a at both ends that are different or all of the above are different Used in combination with 1b, different limit force values can be formed.

In the safety belt reel shown in Figure 4, a torsion bar 1 composed of two sections of torsion bar with different diameters and different effective lengths is installed. Since the torsion bar 1a is provided with a An annular fracture induction groove 1a-1 with a width of L and a depth of D, the torsion fracture section of the torsion bar 1a is a thinner section with a length L corresponding to the fracture induction slot, and the diameter of this section is less than The rod diameter of the torsion bar 1b, so the breaking torque of the torsion bar 1a is smaller than the breaking torque of the torsion bar 1b. After twisting the torsion angle corresponding to its width L, it will break first, causing the torsion bar 1 to break and fail first, and realize the first level of force limitation; the mandrel continues to rotate, and since the torsion bar 1a has been broken, it can only rely on the torsion bar 1b bears the pressure of the webbing, so that the force limiting value of the torsion bar 1 shown is significantly reduced, that is, it enters the second level of force limiting with a smaller force limiting value. That is to say, in this embodiment, through the fracture induction groove 1a-1 provided on the torsion bar 1a, two-stage decreasing force limiting is realized, thereby forming the force limiting characteristic curve as shown in FIG. 7 .

second embodiment

In this embodiment, the torsion bar is integral, please refer to FIG. 5 , which is a schematic structural diagram of the second embodiment of the torsion bar of the present invention. As shown in Figure 4, the torsion bar is integral, and its two ends and the middle are also provided with circumferential external teeth, as shown in Figure 4, the two ends of the external teeth 1-2, 1-3, the middle External teeth 1-1. The middle external teeth 1-1 divide the torsion bar 1 into two torsion bar sections located on both sides thereof: a left bar section 1-a and a right bar section 1-b, and the torsion bar section 1 -A is provided with an annular fracture induction groove coaxial with the torsion bar along the circumferential direction, the depth is D, and the width is L. Other aspects of the structure of the torsion bar of this embodiment and the assembly and cooperation relationship with the safety belt retractor are the same as those of the first embodiment above, and have the same technical effect as the torsion bar of the first embodiment above, here No longer.

third embodiment

The torsion bars of the first embodiment and the second embodiment are only provided with a fracture induction groove on one section of the bar sections on both sides of the outer teeth in the middle circumferential direction. In other embodiments, whether it is a two-section combined Whether it is a torsion bar or an integral torsion bar, multiple fracture induction grooves of different shapes can be set on the two sections on both sides of the outer teeth in the middle at the same time, but no matter how many fracture induction grooves of different shapes are set on it, The force-limiting characteristics of the torsion bar section are only the effective depth and effective width of the fracture induction groove on the bar section. The effective depth is the depth of the fracture induction groove that determines the breaking torque of the torsion bar, and the effective width is the fracture induction groove that determines the torsion fracture angle of the torsion bar. Width; in other words, the effective depth refers to the maximum depth of all fracture induction grooves on the torsion bar, and the effective width refers to the sum of the bottom widths of all the maximum depth fracture induction grooves on the torsion bar. In the first embodiment and the second embodiment, the effective depth of the fracture induction groove of the torsion bar 1a is the groove depth D, and the effective width is the groove width L.

The third embodiment will provide a torsion bar in which a plurality of fracture induction grooves of different shapes are provided on two torsion bar segments at the same time, as shown in Figure 6, which is a schematic diagram of the third embodiment of the present invention, and the safety device shown in Figure 6 A torsion bar 1 composed of two sections of torsion bar 1a and 1b of the same material but with different effective lengths and diameters is installed in the reel. The external teeth at both ends and the external teeth in the middle are end external teeth 1-2, 1-3, middle outer teeth 1-1. Wherein the torsion bar 1a is provided with two fracture induction grooves of different shapes, and the torsion bar 1b is provided with three fracture induction grooves of different shapes. The torsion bar 1a is provided with two annular fracture induction grooves 1a-a, 1a-b coaxial with the torsion bar along its circumferential direction, and the fracture induction groove 1a-a has the largest depth, so the torsion force The effective depth of the fracture induction groove of the rod 1a is the groove depth D _aa of the fracture induction groove 1a-a, and the effective width is the groove bottom width L _aa of the fracture induction groove 1a-a; the fracture induction groove 1b is opened along its circumferential direction There are three annular fracture induction grooves 1b-a, 1b-b, and 1b-c arranged in a ring coaxial with the torsion bar, and the groove depth of 1b-a is the same as the maximum groove depth of 1b-b, and they are all larger than 1b-c The maximum groove depth of the torsion bar 1b is large, so the effective depth of the fracture induction groove of the torsion bar 1b is the groove depth D _ba of the fracture induction groove 1b-a or the maximum depth D _bbMax of the fracture induction groove 1b-b, and the effective width is the fracture induction groove The sum of the groove width L _ba of 1b-a and the groove width L _bbmax of the section corresponding to the maximum depth of the fracture induction groove 1b-b is L _ba +L _bbmax . Since D _aa = D _ba or D _bbMax , the breaking torque of the torsion bar 1a is the same as that of the torsion bar 1b, but L _aa < L _ba + L _bbmax , that is, the torsion deformation bar of the torsion bar 1a The segment length L _aa is shorter than the length L _ba + L _bbmax of the torsion deformation rod section of the torsion bar 1b. When the seat belt retractor mandrel rotates, the torsion deformation rod segment of the torsion bar 1a is shorter, and only need to twist Smaller angles can achieve the amount of deformation required for twisting off, so the smaller angle of torsion breaking will break and fail first, realizing the first level of force limitation; the mandrel continues to rotate, because the torsion bar 1a has been broken, only Relying on the torsion bar 1b to bear the pressure of the webbing, the force limiting value of the torsion bar 1 shown is significantly reduced, that is, enters the second level of force limiting with a smaller force limit value. It can be seen that the torsion bar in this embodiment has the same technical effect as the torsion bar in the above-mentioned first and second embodiments. In addition, other aspects of the structure of the torsion bar in this embodiment and the assembly of the seat belt retractor The cooperation relationship is the same as that of the above two embodiments, and will not be repeated here.

The present invention also protects a safety belt retractor, which uses the torsion bar of the above-mentioned embodiment. As for the technical details of applying the torsion bar to the retractor, the specific structure of the retractor can refer to the embodiment described above for the torsion bar. The description will not be repeated here.

The present invention also protects a seat belt assembly, which uses the seat belt retractor described in the above embodiment, and can obtain the beneficial effects brought by the retractor in the above embodiment. The assembly of the retractor, the webbing and other related spare parts can refer to the existing technology, and will not be discussed here.

Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection should be based on the scope defined by the claims of the present invention.

Claims (11)

1. a kind of torque arm for seat belt retractor, the seat belt retractor includes retractor frame and spool and torsion Bar；The belt retractor frame includes two opposite side walls, and band is respectively arranged in the corresponding position in the two side The round hole of internal tooth；The spool includes the through-hole that set along central axes and is used to wind the mandrel and separably of ribbon It is respectively arranged at two end caps at mandrel both ends；The center of the end cap is provided with central pit hole or through-hole with internal tooth, For fixing the two of the torque arm ends, and the end cap is circumferentially provided with and the internal tooth on the retractor frame Matched external tooth, for spool described in locking；The middle section position of the through-hole of the mandrel axis line position is provided with internal tooth；Institute It is in rod-shaped to state torque arm, and across the through-hole of the mandrel, both ends and middle part are both provided with circumferential external tooth, and the torsion The circumferential external tooth at power bar both ends respectively in the central pit hole or through-hole of described two end caps on the coiler Tooth matches, the internal tooth phase of the circumferential external tooth in the middle part of the torque arm and the middle section position of the through-hole of the mandrel position of center line Cooperation, which is characterized in that at least one section in two sections of rod segments of the circumferential external tooth both sides in the middle part of the torque arm be provided with it is disconnected Induction slot is split, and the fracture induction slot on two sections of torque arms is both provided with scheduled effective depth and effective width, During so that the torque arm being reversed with the mandrel, one section in two sections of torsion rod segments is first broken.

2. the torque arm according to claim 1 for seat belt retractor, which is characterized in that it is described fracture induction slot be Along the annular groove of the circumferencial direction of the torque arm.

3. the torque arm according to claim 2 for seat belt retractor, which is characterized in that it is described fracture induction slot with The torque arm is coaxial.

4. the torque arm according to claim 3 for seat belt retractor, which is characterized in that it is described fracture induction slot be Annular groove.

5. the torque arm according to claim 4 for seat belt retractor, which is characterized in that the fracture of the circular ring shape Induction slot is provided with scheduled groove depth and groove width.

6. the torque arm according to claim 1 for seat belt retractor, which is characterized in that the fracture induction slot Number is one.

7. the torque arm according to claim 1 for seat belt retractor, which is characterized in that the torque arm it is described It is both provided with avoidance hypodontia on the circumferential external tooth at middle part, and avoids the position that tooth lacks and correspond to and ribbon end is passed through and fixed on mandrel Fixing groove.

8. the torque arm according to claim 7 for seat belt retractor, which is characterized in that the torque arm is by two sections Torque arm docks in an axial direction, and the both ends of every section of torque arm are both provided with circumferential external tooth, and two sections of torque arms dock end The circumferential external tooth tooth form position of fixing groove that aligns and passed through on corresponding to mandrel and fix ribbon end be provided with Avoid hypodontia；The circumferential external tooth of two sections of torque arms docking end collectively forms the circumferential external tooth in the middle part of the torque arm；Institute The avoidance hypodontia stated on the circumferential external tooth of two sections of torque arm docking ends is collectively formed on the circumferential external tooth in the middle part of the torque arm Avoidance hypodontia.

9. the torque arm according to claim 8 for seat belt retractor, which is characterized in that two sections of torque arms Diameter, material, at least one of difference of effective length.

10. a kind of seat belt retractor, which is characterized in that the torque arm is turned round for 1 to 9 any one of them of the claims Power bar.

11. a kind of safety belt assembly, which is characterized in that use the seat belt retractor described in the claims 10.