Seat belt retractor for a seat belt device of a motor vehicle

Abstract

The invention relates to a belt retractor (1) for a seat belt device of a motor vehicle, comprising: a rotatably mounted belt reel (5) on which a belt of the belt device can be wound; and a reversible belt tensioner having a drive wheel (20) which, when activated, drives the belt reel (5) in the winding direction via the drive wheel (20); and a forcibly controlled tensioner coupling which transmits a drive movement from the drive wheel (20) to the belt reel (5), the forcibly controlled tensioner coupling having at least one coupling pawl (21) and a control element (22), the at least one coupling pawl is mounted on the drive wheel (20) and can be moved into and out of engagement with a toothing (231) fixed on the seatbelt reel in order to produce and release a rotational connection of the drive wheel (20), and a control element (223) having a first control profile (223), the drive wheel (20) has a first control profile for controlling an engagement movement of the coupling pawl (21) into a toothing (231) fixed to the belt reel, a force transmission surface (201) extending in a radial direction being provided on the drive wheel (20) and being arranged such that the coupling pawl (21) comes into contact with the end-side contact surface (217) by means of the engagement movement into the toothing (231) fixed to the belt reel.

Description

[0001] The present invention relates to a seat belt retractor for a seat belt device of a motor vehicle, the seat belt retractor having the features of the preamble according to claim 1.

[0002] The seat belt retractor is used in a seat belt device of a motor vehicle and serves to wind up one end of a seat belt provided for restraining an occupant. The seat belt retractor is fastened to the vehicle structure or to a vehicle seat of the vehicle structure or to a bench seat fastened thereto. The seat belt retractor has, in its basic structure, a frame provided for fastening purposes and a seat belt reel rotatably mounted in the frame, wherein the seat belt can be wound around the seat belt reel. The seat belt reel is spring-loaded via a spring in the winding direction and, in the case of an acceleration of the seat belt pull-out exceeding a pre-determined value or a deceleration of the vehicle, the further pull-out of the seat belt can be blocked by means of a locking device, so that the occupant is then restrained before hitting the interior structure of the vehicle in order to prevent serious injuries.

[0003] In order to reduce the occupant load during restraint, it has proven advantageous to provide force limiting devices which, in the case of the seat belt reel being blocked and a seat belt pull-out force exceeding a pre-determined value, allow a force-limited rotation of the seat belt reel in the pull-out direction and thus a force-limited forward displacement of the occupant. Since the reduction of the occupant load thus achieved is directly related to the available forward displacement path, it has been found advantageous to tighten the slack seat belt present in the seat belt by means of a seat belt pretensioner before activating the force limiting device in order to increase the available forward displacement path and to associate the occupant with the vehicle deceleration as early as possible.

[0004] In seat belt pretensioners, a distinction is made between reversible seat belt pretensioners and irreversible seat belt pretensioners or even performance pretensioners. Reversible seat belt pretensioners have a lower pretensioning capacity of approximately 100 N to 800 N and are used to tighten a slack seat belt in the event of a danger in order to prepare for a possible subsequent accident. If no accident subsequently occurs, the seat belt will slacken again. Electric motors which can be controlled particularly well and reversibly have proven successful for driving reversible seat belt pretensioners. Irreversible seat belt pretensioners have a higher pretensioning capacity of 400 N to 2000 N and are only activated when an accident can no longer be avoided, i.e. in the early stages of an accident. Thus, irreversible seat belt pretensioners are always activated after reversible seat belt pretensioners. Pyrotechnic drives which cannot be activated again after a single activation have proven to be drives for irreversible seat belt pretensioners, so that in this case the entire seat belt device with an irreversible seat belt pretensioner must be replaced.

[0005] In this case, the seatbelt pretensioner can be engaged at different positions of the seatbelt, for example, engaged at the seatbelt buckle, the end fitting, or even engaged at the seatbelt retractor. When the seatbelt pretensioner is used on the seatbelt retractor, the seatbelt pretensioner suddenly drives the seatbelt spool in the winding direction when activated and thereby tightens the slack seatbelt present in the seatbelt. In the sense of the present invention, the term "seatbelt pretensioner" is only understood as a seatbelt pretensioner arranged on the seatbelt retractor and driving the seatbelt spool. Since the seatbelt spool must be able to rotate freely substantially during normal use for buckling and unbuckling the seatbelt, the drives of reversible seatbelt pretensioners and irreversible seatbelt pretensioners are only connected to the seatbelt spool via couplings when activated. The couplings are designed to ensure that they do not inadvertently establish a rotational connection, otherwise the normal use of the seatbelt retractor would be hindered due to the rotational movement of the seatbelt spool being disturbed.

[0006] Since in the case of no subsequent accident, the reversible seatbelt pretensioner should be deactivated again and the seatbelt retractor should be used normally again, the couplings of the reversible seatbelt pretensioner must also be designed to be reversible. In addition, when a subsequent accident occurs and the irreversible seatbelt pretensioner is activated, the couplings of the reversible seatbelt pretensioner must also be intentionally disengaged so that the driving movement of the irreversible seatbelt pretensioner is not disturbed by the still engaged couplings of the reversible seatbelt pretensioner.

[0007] In addition, the couplings of different seatbelt pretensioners must be designed such that they automatically establish a rotational connection between the drive and the seatbelt spool when the drive device is activated, which can be achieved, for example, by friction, by inertial forces, or by a control profile. Thereby, the movement of the coupling is actively controlled by the initial movement of the drive.

[0008] Therefore, on the one hand, the coupling needs to automatically perform the coupling movement when the drive device is activated, but in other cases, intentionally not perform the coupling movement in order to prevent an undesired coupling connection.

[0009] For example, a seatbelt retractor with a reversible seatbelt pretensioner is known from the applicant's document DE 10059227 C1. The seatbelt pretensioner has a friction-controlled coupling with two coupling pawls and a braking element. The coupling pawls are slidably mounted on the drive wheel and, in order to establish a coupling connection, engage in the internal teeth of a clutch bell that is rotationally fixed to the seatbelt shaft.

[0010] From DE 10 2014 009 038 B4, a coupling for a seat belt tensioner is also known, which has two coupling pawls mounted on a drive wheel, which is referred to herein as the input element. To establish the coupling connection, the coupling pawls engage in the external teeth of an output element connected to the seat belt reel. To control the movement of the coupling element, a control element coupled to an inertial mass is provided, on which an input control geometry and an output control geometry for controlling the movement of the coupling pawls are provided.

[0011] In this context, the object of the present invention is to provide a seat belt retractor of a general type in which the transmission of the driving movement of the drive wheel to the seat belt shaft is further improved.

[0012] To achieve this object, a seat belt retractor having the features described in claim 1 is proposed. Further preferred embodiments of the present invention can be gathered from the dependent claims, the drawings and the associated description.

[0013] According to the basic concept of the present invention, it is proposed to provide a force transmission surface extending in the radial direction on the drive wheel, which is arranged such that the coupling pawl abuts against the force transmission surface with its end face contact surface due to the engagement movement into the teeth, and the drive wheel drives the coupling pawl into the teeth fixed to the seat belt reel in the engaged position, so as to transmit the rotational movement to the seat belt reel via the force transmission surface while applying a compressive force in the circumferential direction of the drive wheel.

[0014] Due to the provision of the force transmission surface extending in the radial direction on the drive wheel and the driving of the coupling pawl achieved on this force transmission surface (the driving is transmitted to the seat belt reel through the engagement of the coupling pawl in the teeth in rotationally fixed connection with the seat belt reel), the driving force is transmitted from the drive wheel to the coupling pawl and the seat belt reel more immediately and thus more directly. In this case, by distributing the bearing force between the rotary joint and the force transmission surface extending in the radial direction, the bearing force to be absorbed by the coupling pawl on the drive wheel in the rotary joint is reduced at the same time. Ideally, the driving torque can even be transmitted without bearing loads on the coupling pawl by arranging the rotary joint such that it lies outside the force transmission path from the force transmission surface via the coupling pawl to the teeth fixedly arranged on the seat belt reel.

[0015] It is further proposed that the force transmission surface has an inclined portion in the radial direction with respect to the axis of rotation of the drive wheel, and this inclined portion is aligned with the teeth of the tooth portion fixed to the seat belt reel. Since the alignment of the proposed force transmission surface is with respect to the teeth of the tooth portion fixed to the seat belt reel, the teeth form a reaction surface for transmitting force in the same direction, such that the force vector is also in the same direction during the transmission of force from the drive wheel to the coupling pawl and from the coupling pawl to the tooth portion fixed to the seat belt reel. This allows for optimizing the force transmission conditions, especially with respect to avoiding sliding of the force transmission surface as much as possible.

[0016] It is further proposed that the force transmission surface is arranged such that the coupling pawl resting thereon is arranged not to contact the first control profile. This means that the first control profile is not loaded during the reversible seat belt tensioning during the driving of the seat belt reel. This also ensures that the force transmission occurs only via the force transmission surface of the drive wheel, the end face contact surface of the coupling pawl, and the bearing of the coupling pawl in the rotary joint.

[0017] It is further proposed that at least one first tooth is provided on the coupling pawl, and the coupling pawl engages in the tooth portion fixed to the seat belt reel by means of this first tooth in the engaged position. The coupling pawl thus has a profile that matches the tooth portion fixed to the seat belt reel, where the tooth geometry of the first tooth on at least one tooth face corresponds to the tooth face of the tooth portion fixed to the seat belt reel.

[0018] It is further proposed that the end face of the tooth facing the tooth portion fixed to the seat belt reel is oriented such that the angle between the end face of the tooth and the radially outward-facing end face of the tooth of the tooth portion is less than 30 degrees. Due to the alignment of the proposed end face of the tooth with the end face of the tooth of the tooth portion fixed to the seat belt reel, in the case of tooth-to-tooth contact, the tooth slides off the tooth of the tooth portion fixed to the seat belt reel with a very small compressive force without getting stuck.

[0019] It is further proposed that at least one second tooth is provided, and the first tooth or the second tooth is designed to form an enlarged latching tooth, and the coupling pawl uses this latching tooth to first engage with the tooth portion fixed to the seat belt reel during the engaging movement. The enlarged latching tooth first engages with the tooth portion fixed to the seat belt reel, and thereby causes a pre-alignment of the coupling pawl with the tooth portion fixed to the seat belt reel, such that the other tooth then engages in the tooth portion fixed to the seat belt reel in a defined alignment manner without being blocked itself in the case of tooth-to-tooth contact.

[0020] In this case, the latching tooth is preferably formed by the first tooth adjacent to the end face contact surface. Thus, the coupling pawl is pulled into the tooth portion fixed to the seat belt reel starting from the end facing the end face contact surface.

[0021] It is further proposed that a first control pin is provided on the coupling pawl, and the coupling pin slides on a first control profile by means of this control pin during the engagement movement. The coupling pawl together with the first control pin bears against the first control profile, and the first control profile defines the path of the engagement movement of the coupling pawl in the teeth fixed to the seat belt reel by its shape, in such a way that the first control pin slides on the teeth.

[0022] It is further proposed that the first control profile has a stop portion oriented in the circumferential direction, and the first control pin is arranged on the coupling pawl such that it is arranged radially inward relative to the stop portion in the engagement position of the coupling pawl. Due to the stop portion of the first control profile, during the tooth engagement during reversible pretensioning, the coupling pawl is blocked to prevent a radially outwardly directed control movement from the teeth fixed to the seat belt reel.

[0023] It is further proposed that the first control profile is formed by a spring arm fixed at one end to the control element, and the first control pin slides on the spring arm from the fixed end to the free end during the engagement movement of the coupling pawl. By designing the first control profile as a spring arm and its proposed arrangement, the control pin and the coupling pawl can perform a slight radial movement relative to the first control profile during the engagement movement. This can prevent the movement from being inhibited due to inaccurate shape or different frictional forces.

[0024] It is further proposed that a second control profile is provided on the control element for controlling the disengagement movement of the coupling pawl. The second control profile controls the disengagement movement of the coupling pawl by the separate shape of the second control profile in its path, independently of the engagement movement of the coupling pawl.

[0025] In this case, a second control pin can preferably be provided on the coupling pawl, and the coupling pin slides on the second control profile by means of this control pin during the disengagement movement.

[0026] It is further proposed that a stop profile is provided on the control element, and this stop profile forms a stop for the coupling pawl in the engaged position. After the end of the engagement movement, the stop profile defines the final position of the coupling pawl. In addition, this limits any further differential movement of the control profile relative to the coupling pawl.

[0027] It is further proposed that the blocking profile has a first blocking surface oriented in the radial direction and a second blocking surface oriented in the circumferential direction, wherein the first blocking surface forms a stop and radially outwardly pushes the coupling pawl during the rotational movement of the tooth portion in the winding direction of the seat belt, and forces the control element to perform a relative movement by the compressive force applied by the first control pin on the spring arm thereby, during which relative movement, the second control pin slides from the first blocking surface onto the second blocking surface, wherein the second blocking surface prevents the coupling pawl from performing a radially inwardly directed pivoting movement into the tooth portion fixed on the seat belt reel. The proposed solution means that when the irreversible seat belt pretensioner is activated and thereby the seat belt reel rotates in the winding direction, the coupling pawl is automatically pushed out of the engaged position and the coupling connection is released. Additionally, the coupling pawl is simultaneously blocked by a support on the second blocking surface to prevent repeated engagement movements in the tooth portion fixed on the seat belt reel.

[0028] It is further proposed that the coupling pawl has a curved arc shape and is arranged such that the shorter side of the arc faces the tooth portion fixed on the seat belt reel. The curved coupling pawl thus engages around the tooth portion fixed on the seat belt reel and is formed with a curved shorter side or also the inner side which is a force transmission surface. For this purpose, the inner force transmission surface can be provided with one or more teeth, for example.

[0029] In this regard, it is further proposed that the coupling pawl is pivotally mounted in a pivot bearing which is arranged at the end of the coupling pawl remote from the end face contact surface. During the pivoting movement, the coupling pawl pivots radially inwardly together with the end face contact surface and in doing so contacts the force transmission surface of the drive wheel through the contact surface.

[0030] The present invention will be explained below using preferred embodiments with reference to the accompanying drawings. In the drawings:

[0031] Figure 1 is a seat belt retractor with a reversible seat belt pretensioner; and

[0032] Figure 2 is a drive wheel with a pretensioner coupling and a housing part for transmitting the rotational movement of the reversible seat belt pretensioner; and

[0033] Figure 3 is the drive wheel, the coupling pawl and the tooth portion fixed on the seat belt reel during the engagement movement; and

[0034] Figure 4 is the drive wheel, the coupling pawl and the tooth portion fixed on the seat belt reel in the disengaged position; and

[0035] Figure 5is the drive wheel, coupling pawl and tooth part fixed to the seat belt reel in the engaged position; and

[0036] Figure 6 is the drive wheel, coupling pawl and tooth part fixed to the seat belt reel in the first contact position during the engaging movement; and

[0037] Figure 7 is the drive wheel, coupling pawl and tooth part fixed to the seat belt reel in the tooth-to-tooth position of the first tooth during the engaging movement; and

[0038] Figure 8 is an enlarged view of the drive wheel, coupling pawl and tooth part fixed to the seat belt reel in the tooth-to-tooth position of the first tooth during the engaging movement; and

[0039] Figure 9 is the drive wheel, coupling pawl and tooth part fixed to the seat belt reel in different positions during the activation of the irreversible seat belt pretensioner.

[0040] Figure 1 Shows a seat belt retractor 1 according to the present invention, which has a reversible seat belt pretensioner 3, a drive wheel 20, a pretensioner coupler 2 and a winding unit 4. The winding unit 4 includes a seat belt reel 5 and an irreversible pyrotechnic seat belt pretensioner 7 or a power pretensioner as basic components, and the seat belt reel is rotatably mounted in a frame 6 having an axial extension 8.

[0041] The reversible seat belt pretensioner 3 is activated in the situation before an accident and is used to tighten the seat belt to prepare for a possible accident. The seat belt is tightened with a pulling force of 100 N to 800 N, and the pretensioning force can be selected at different levels according to the specifications of the vehicle manufacturer or can be designed in stages according to various pre-accident specific criteria so that the pretensioning force increases gradually.

[0042] The irreversible seat belt pretensioner 7 is only activated when an accident can no longer be avoided or at the very beginning of an accident, and causes a greater increase in the tension in the seat belt of 400 N to 2000 N compared to the increase in tension when the reversible seat belt pretensioner 3 is activated. Therefore, when the irreversible seat belt pretensioner 7 is activated, the seat belt reel 5 is driven with a much larger torque than when the reversible seat belt pretensioner 3 is activated.

[0043] The reversible seat belt pretensioner 3 includes an electric motor and a gearbox, and the gearbox has a gear mechanism installed therein, and the gear mechanism transmits the rotational driving movement of the electric motor to the drive wheel 20.

[0044] As Figure 2The toothed ring 23 shown is held in a rotationally fixed manner on the extension 8 of the seat belt reel 5. The toothed ring 23 has a radially outer toothing which forms, in the fastening position of the toothed ring 23 on the extension 8, a toothing 231 fixed to the seat belt reel.

[0045] As Figure 2 shown, the housing part 25 is arranged on the gearbox of the reversible seat belt tensioner 3, in which the drive wheel 20 is rotatably mounted. For this purpose, the housing part 25 has an annular axially extending part 251 which passes through a central bearing opening in the drive wheel 20. Furthermore, a control element 22 is provided which has an annular spring 221 and a plate element 222 fixed via the annular spring 221, which plate element is frictionally fixed to the axially extending part 251 by means of the annular spring 221. In addition, an arcuate coupling pawl 21 is provided which has, on one of its ends, a bearing pin 211 projecting on both sides. Furthermore, an annular cover disc 24 is provided which has a bearing opening 241, on one side of which the coupling pawl 21 is mounted by means of the bearing pin 211, while the other side of the bearing pin 211 engages in a bearing opening (not visible) of the drive wheel 20. Thus, both sides of the coupling pawl 21 are mounted in the drive wheel 20 and in the cover disc 24.

[0046] The toothed ring 23 and the coupling pawl 21 are arranged such that the coupling pawl 21 faces the toothing 231 fixed to the seat belt reel with its shorter radially inner side 219 and encloses this toothing, as Figure 3 and Figure 4 shown. The coupling pawl 21 has, on its shorter inner side 219, a toothing which is formed by a first tooth 214, a second tooth 215 and a third tooth 216. The teeth 214, 215 and 216 of the coupling pawl 21 thus face the toothing 231 fixed to the seat belt reel. Furthermore, the coupling pawl 21 has, at its end remote from the bearing pin 211 and facing the first tooth 214, an end face contact surface 217 which is opposite the force transmission surface 201 of the drive wheel 20.

[0047] A first control profile 223 and a second control profile 224 are provided on the plate part 222 of the control element 22, as Figure 3 and Figure 4 shown. The first control profile 223 is realized by the radially inner edge side of a bent spring arm 228, one end of which is fixed to the plate part 222. The second control profile 224 is formed by the bent upper edge side of a projection protruding axially from the plate part 222. In addition, as Figure 5As shown, an axially protruding stop profile 225 is provided on the plate part 222, which has a first stop surface 226 aligned radially and a second stop surface 227 aligned circumferentially. The coupling pawl 21 is provided with a first axially protruding control pin 212 and a second axially protruding control pin 213, which axially protrude from the side of the plate part 222 of the coupling pawl 21 facing the control element 22 in the installed position. Conversely, the plate part 222 of the control element 22 is aligned such that the side with the two control profiles 223 and 224 faces the side of the coupling pawl 21 where the control pins 212 and 213 are arranged.

[0048] In Figures 6 to 8 , the coupling pawl 21 is enlarged and can be seen in different positions during the engagement movement in the teeth 231 of the toothed ring 23 fixed to the seat belt reel. As Figure 6 shown, the first tooth 214 is enlarged, shaped and aligned such that it first engages into the teeth 231 fixed to the seat belt reel during the engagement movement. The first tooth 214 is the tooth adjacent to the end face contact surface 217 of the coupling pawl 21, and is thus the foremost tooth of the coupling pawl 21. Therefore, the first tooth 214 is arranged at the end of the coupling pawl 21 further away from the bearing pin 211, and during the pivoting movement of the coupling pawl 21, it performs the largest pivoting path compared to the other teeth 215 and 216. During the engagement movement, the coupling pawl 21 first engages with the first tooth 214 in the teeth 231 fixed to the seat belt reel, whereby the coupling pawl 21 is pre-aligned relative to the teeth 231 fixed to the seat belt reel. The first tooth 214 thus serves as a catch tooth. Due to the pre-alignment of the coupling pawl 21, it then engages with the teeth 231 fixed to the seat belt reel through the additional teeth 215 and 216, and the engagement movement is not blocked tooth-to-tooth by the additional teeth 215 and 216.

[0049] If, during the engagement movement in the teeth 231 fixed to the seat belt reel, the coupling pawl 21 strikes the radially outer end face of the teeth of the teeth 231 fixed to the seat belt reel with its first tooth 214 in a tooth-to-tooth situation as Figure 7 shown, the engagement movement is briefly disturbed. Due to the enlarged design of the first tooth 214 as a catch tooth, the other teeth 215 and 216 are intentionally not yet in contact with the teeth 231 fixed to the seat belt reel, such that the tooth-to-tooth instance is intentionally limited to the contact of the first tooth 214.

[0050] As in Figure 8As can be seen in the enlarged view, the first tooth 214 is shaped on its radially inner end face such that the end face of the first tooth 214 and the end faces of the adjacent teeth of the tooth portion 231 fixed to the seat belt reel enclose an angle W of less than 30 degrees in the circumferential direction. Thus, the first tooth 214 slides along the end faces of the teeth of the tooth portion 231 fixed to the seat belt reel without obstructing the movement. After the first tooth 214 has slid out, the first tooth engages with the next tooth of the tooth portion 231 fixed to the seat belt reel in the subsequent gap, and the engaging movement of the coupling pawl 21 ends.

[0051] In Figure 4 it is possible to see the coupling pawl 21 in the pivotally disengaged position. Starting from this position, the engaging movement of the coupling pawl 21 is triggered by driving the drive wheel 20 in the direction of the arrow S in Figure 3 . Due to the driving movement of the drive wheel 20, the coupling pawl 21 also rotates in the direction of the arrow S. In this case, the coupling pawl 21 with the first control pin 212 abuts against the radially inclined inwardly directed control section 2232 of the first control profile 223, and the first control pin 212 of the coupling pawl 21 then slides along this control section during further rotational movement. By the sliding of the first control pin 212 along the control section 2232 of the first control profile 223, the coupling pawl 21 is forced to perform a radially inwardly directed engaging movement in the direction of the tooth portion 231 fixed to the seat belt reel, wherein the path of this engaging movement is predetermined by the shape and alignment of the control section 2232. When the coupling pawl 21 contacts the force transmission surface 201 of the drive wheel 20 through its end face contact surface 217, the pivoting movement of the coupling pawl terminates. In Figure 3 this position of the coupling pawl 21 can be seen. To complete the engaging movement of the coupling pawl 21, the coupling pawl is then further displaced relative to the toothed ring 23 and the plate portion 222 in the direction of the arrow S on the force transmission surface 201 by the drive wheel 20 until it contacts the first stop surface 226 of the stop profile 225 through the second control pin 213. Thus, the first stop profile 225 together with the first stop surface 226 forms a stop for the movement of the coupling pawl 21. At the same time, the coupling pawl 21 together with the first control pin 212 moves to a position where the first control pin 212 is arranged radially inward relative to the stop portion 2231 of the first control profile 223. Thus, the coupling pawl 21 is subsequently fixed to prevent accidental pivoting out from the tooth portion 231 fixed to the seat belt reel. Furthermore, in Figure 5 this engaged position visible in, the coupling pawl 21 abuts against the teeth of the tooth portion 231 fixed to the seat belt reel in a force-transmitting manner by means of the teeth 214, 215 and 216.

[0052] The force transmission surface 201 of the drive wheel 20 is radially outwardly inclined and forms an angle E1 of approximately 15 degrees to 30 degrees with the radial direction opposite to the driving direction of the drive wheel 20 in the direction of the arrow S. The end face contact surface of the coupling pawl 21 is aligned in such a way that, in the engaged position of the coupling pawl, the coupling pawl is aligned with the radial direction at the same angle E1 and bears flat against the force transmission surface 201 of the drive wheel 20. The tooth flanks of the teeth of the tooth part 231 fixed to the seat belt reel and the opposite tooth flanks of the teeth 214, 215 and 216 of the coupling pawl 21 in the engaged position are aligned in the same direction as the angle E1 of the force transmission surface, and also enclose an angle E2 to E4 of approximately 15 degrees to 30 degrees in the direction opposite to the driving direction of the drive wheel 20 in the direction of the arrow S, such that the force vectors F1 to F4 on the force transmission surface 201 point radially outward to the end face contact surface 217 and from the teeth of the tooth part 231 fixed to the seat belt reel to the teeth 214, 215 and 216. The angles E1 to E4 do not have to be the same. They only have to be in the same direction with respect to the radial direction and inclined with respect to the driving direction such that the force vectors F1 to F4 point in the same circumferential direction in the direction of the driving rotational movement in the direction of the arrow S. This can counteract the tendency of the tooth flanks and the end face contact surface 217 to slip off the force transmission surface 201 of the drive wheel 20. The force transmission surface 201 is part of the shape-stable contour of the drive wheel 20 and thus forms a shape-stable abutment for the coupling pawl 21 in the Figure 3 adjacent positions. The coupling pawl 21 bears flat against the force transmission surface 201 with its end face contact surface 217.

[0053] Therefore, the driving force is directly transmitted from the drive wheel 20 via the coupling pawl 21 to the tooth part 231 fixed to the seat belt reel of the toothed ring 23 and further transmitted to the seat belt reel 5. Thus, the bearing force FL absorbed by the bearing of the coupling pawl 21 via the bearing pin 211 can be reduced. Ideally, the coupling pawl 21 is pulled onto the tooth part 231 and thereby aligns the drive wheel 20 to such an extent that the bearing force in the bearing of the drive wheel 20 is reduced to 0. Advantageously, the bearing of the coupling pawl 21 on the bearing pin 211 is arranged at the end remote from the end face contact surface 217, such that the coupling pawl 21 introduces the torque applied by the force transmission surface 201 into the tooth part 231 fixed to the seat belt reel, while the bearing of the coupling pawl 21 is not tensioned as it is not located in the force transmission path from the force transmission surface 201 via the contact surface 217 to the tooth part 231 fixed to the seat belt reel.

[0054] If the pre-accident situation has ended and has not turned into an accident, the reversible seat belt tensioning also stops and the tension in the seat belt is reduced. For this purpose, the drive wheel 20 rotates against the driving direction in Figure 4in the direction of arrow A for a short time, whereby the coupling pawl 21 with the first control pin 212 rotates in the circumferential direction to such an extent that the first control pin 212 is no longer arranged radially inwards in the blocking part 2231 of the first control contour 223. At the same time, the coupling pawl 21 contacts the second control contour 224 with the second control pin 213. The second control contour 224 is curved and points radially outwards, such that the coupling pawl 21 slides off this second control contour during a further rotational movement of the drive wheel 20 in the direction of arrow A and is pulled radially outwards until this second control contour is again arranged in the disengaged position, as Figure 4 shown.

[0055] If the pre-accident situation turns into an accident, the irreversible seatbelt pretensioner 7 is activated and the seatbelt shaft 5 together with the toothed ring 23 and the toothing 231 fixed to the seatbelt reel is suddenly driven in the winding direction, which is shown by the direction of arrow S in the Figure 9 left side view of. At the start of the drive movement of the drive wheel 20, the coupling pawl 21 is still in the engaged position, which corresponds to the Figure 5 position of the coupling pawl 21 in. Due to the rotational movement of the toothed ring 23, the teeth of the toothing 231 fixed to the seatbelt reel slide over the teeth 214, 215 and 216, and the coupling pawl 21 is pushed radially outwards, wherein the first control pin 212 radially displaces the spring arm 228 outwards, and the second control pin 213 moves radially outwards on the first stop surface 226 of the stop contour 225, as can be seen in the Figure 9 middle illustration of. Due to the deformation of the spring arm 228, a circumferential force is exerted on the plate element 222 of the control element 22, which displaces the plate element 222 in the direction of arrow R as soon as the second control pin 213 no longer abuts laterally against the first stop surface 226. By displacing the plate element 222, this plate element together with the second stop surface 227 of the stop contour 225 moves into a position that radially supports the second control pin 213 on the inside. In addition, the first control pin 212 overcomes the spring arm 228, such that the spring arm springs back to the first control pin 212 and prevents the first control pin from moving backwards, as Figure 9 shown in the right side view of. Subsequently, the connection between the reversible seatbelt pretensioner 3 and the seatbelt reel 5 is released, and the irreversible seatbelt pretensioner 7 can drive the seatbelt reel 5 without interference from the reversible seatbelt pretensioner 3.

[0056] The coupling pawl 21 is subsequently irreversibly prevented from pivoting backwards into the engaged position, but this is harmless to the function of the seatbelt retractor, since the seatbelt retractor must in any case be replaced after activation of the irreversible seatbelt pretensioner 7.

Claims

1. A seat belt retractor (1) for a seat belt device of a motor vehicle, the seat belt retractor comprising: - a rotatably mounted seat belt spool (5) around which the seat belt of the seat belt device can be wound; and - a reversible seat belt tensioner having a drive wheel (20) which, when activated, drives the seat belt spool (5) in the winding direction via the drive wheel (20); and - an actively controlled tensioner coupling which transfers the driving movement from the drive wheel (1) to the seat belt spool (5), the actively controlled tensioner coupling having: - at least one coupling pawl (21) mounted on the drive wheel (20) which, for establishing and disconnecting the rotational connection of the drive wheel (20), can be moved into and out of engagement with a toothing (231) fixed to the seat belt spool; and - a control element (22) having a first control profile (223) for controlling the engagement movement of the coupling pawl (21) in the toothing fixed to the seat belt spool (231), characterized in that - a force transmission surface (201) extending in the radial direction is provided on the drive wheel (20) and arranged such that the coupling pawl (21) contacts a front-side contact surface (217) by means of the engagement movement in the toothing (231) fixed to the seat belt spool, and - the drive wheel (20) drives the coupling pawl (21) in the engaged position into the toothing fixed to the seat belt spool (231) to transfer the rotational movement to the seat belt spool (5) via the force transmission surface (201) while applying a compressive force in the circumferential direction of the drive wheel (20).

2. The seat belt retractor (1) according to claim 1, characterized in that - the force transmission surface (201) has an inclination in the radial direction relative to the rotational axis of the drive wheel (20), the inclination being aligned with the teeth of the toothing (231) fixed to the seat belt spool.

3. The seat belt retractor (1) according to claim 1 or 2, characterized in that - the force transmission surface (201) is arranged such that the coupling pawl (21) resting thereon in the engaged position is arranged not to contact the first control profile (223).

4. The seat belt retractor (1) according to any one of claims 1 to 3, characterized in that - at least one first tooth (214) is provided on the coupling pawl (21), the coupling pawl (21) engaging in the toothing (231) fixed to the seat belt spool in the engaged position by means of the first tooth.

5. The seat belt retractor (1) according to claim 4, characterized in that - The end face of the first tooth (214) facing the tooth portion (231) fixed to the seat belt reel is oriented such that the angle (W) between the end face of the first tooth (214) and the radially outward-facing end face of the tooth of the tooth portion (231) fixed to the seat belt reel is less than 30 degrees.

6. The seat belt retractor (1) according to any one of claims 4 or 5, characterized in that - at least one second tooth (215, 216) is provided, and - the first tooth or the second tooth (214, 215, 216) is designed as an enlarged detent tooth, and the coupling pawl (21) engages with the tooth portion (231) fixed to the seat belt reel by means of the detent tooth during the engagement movement.

7. The seat belt retractor (1) according to claim 6, characterized in that - the detent tooth is formed by the first tooth (214) adjacent to the contact surface (217).

8. The seat belt retractor (1) according to any one of claims 1 to 7, characterized in that - a first control pin (212) is provided on the coupling pawl (21), and the coupling pawl slides on a second control profile (223) by means of the control pin during the engagement movement.

9. The seat belt retractor (1) according to claim 8, characterized in that - the first control profile (223) has a blocking portion (2231) oriented in the circumferential direction, and - the first control pin (212) is arranged on the coupling pawl (21) such that it is in the engagement position of the coupling pawl (21), and the control pin is arranged radially inwardly with respect to the blocking portion (2231).

10. The seat belt retractor (1) according to any one of claims 8 or 9, characterized in that - the first control profile (223) is formed by a spring arm (228) fixed at one end to the control element (22), and - the first control pin (212) slides on the spring arm (228) from the fixed end to the free end during the engagement movement of the coupling pawl (21).

11. The seat belt retractor (1) according to any one of claims 1 to 10, characterized in that - a second control profile (224) for controlling the disengagement movement of the coupling pawl (21) is provided on the control element (22).

12. The seat belt retractor (1) according to claim 11, characterized in that - a second control pin (213) is provided on the coupling pawl (21), and the coupling pin slides on the second control profile (224) by means of the control pin during the engagement movement.

13. The seat belt retractor (1) according to any one of claims 1 to 12, characterized in that - a blocking profile (225) is provided on the control element (22), and the blocking profile forms a stop for the coupling pawl (21) in the engaged position.

14. The seat belt retractor (1) according to any one of claims 8 or 10, according to any one of claims 11 or 12, and according to claim 13, characterized in that, - the stop profile (225) has a first stop surface (226) oriented in the radial direction and a second stop surface (227) oriented in the circumferential direction, wherein - the first stop surface (226) forms the stop, and - in the case of the rotational movement of the tooth portion (231) fixed to the seat belt reel, the coupling pawl (21) is radially pushed outwards in the winding direction, and - via the compression force applied by the first control pin (212) to the spring arm (228) thereby, the control element (22) is forced to perform a relative movement during which the second control pin (213) slides from the first stop surface (226) onto the second stop surface (227), wherein - the second stop surface (227) prevents the coupling pawl (21) from pivoting radially inwards into the tooth portion fixed to the seat belt reel (231).

15. The seat belt retractor (1) according to any one of claims 1 to 14, characterized in that, - the coupling pawl (21) has an arcuate bent shape and is arranged such that the shorter side (219) of the arc faces the tooth portion fixed to the seat belt reel (231).

16. The seat belt retractor (1) according to claim 15, characterized in that, - the coupling pawl (21) is pivotally mounted in a pivot bearing (211), the pivot bearing being arranged at the end of the coupling pawl (21) remote from the end face contact surface (217).

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