Belt retractor for a seat belt of a motor vehicle

Abstract

The invention relates to a belt retractor for a seatbelt of a motor vehicle, comprising a belt shaft (2) which is rotatably mounted in a housing frame (1), a profiled head (3) which can be locked relative to the housing frame (1), a multi-stage first force-limiting device (4), wherein the first force-limiting device (4) is coupled to the profiled head (3) and to the belt shaft (2), wherein the first force-limiting device (4) allows a force-limited relative rotation of the belt shaft (2) with respect to the locked profiled head (3), and comprising at least one second force-limiting device (5), wherein, in an initial state, the second force-limiting device (5) is decoupled, so that the force-limited relative rotation of the belt shaft (2) with respect to the locked profile head (3) takes place without a force-limited involvement of the second force-limiting device (5).

Description

[0001] Belt retractor for a motor vehicle safety belt

[0002] Description

[0003] The present invention relates to a belt retractor for a safety belt of a motor vehicle, with a belt shaft rotatably mounted in a housing frame, a profile head lockable relative to the housing frame, a multi-stage first force limiting device, wherein the first force limiting device can be coupled on the one hand to the profile head and on the other hand to the belt shaft and wherein the first force limiting device enables a force-limited relative rotation of the belt shaft relative to the locked profile head, and a second force limiting device.

[0004] A belt retractor with the aforementioned features is known, for example, from WO 2020 021 003 A1. A multi-stage first force-limiting device comprises two torsion bars that can be decoupled from each other to set different force-limiting levels. Furthermore, a second force-limiting device is provided, which is coupled to the first multi-stage force-limiting device in an initial state and can be actively decoupled from the multi-stage first force-limiting device. With such a belt retractor, three force-limiting levels can be set for the force-limited relative rotation of the belt shaft.

[0005] The object of the present invention is to eliminate the disadvantages described with reference to the prior art and, in particular, to provide a belt retractor in which the force-limited relative rotation of the belt shaft relative to the locked profile head is possible with multiple force limitation levels. A solution to this problem is provided by the belt retractor having the features of independent claim 1, with further solutions and advantageous developments being specified in the dependent claims and in the description, with individual features of the advantageous developments being combinable with one another in a technically expedient manner.

[0006] The object is achieved in particular by a belt retractor with the features mentioned at the outset, in which the second force limiting device is decoupled in an initial state, so that the force-limited relative rotation of the belt shaft with respect to the locked profile head can take place without force-limiting participation of the second force limiting device.

[0007] In other words, the basic concept of the invention provides that the second force-limiting device is not directly or indirectly connected to the belt shaft in the initial starting state, so that without intentional activation of the second force-limiting device, the force-limited relative rotation of the belt shaft is effected solely by at least one force-limiting element of the first force-limiting device. Thus, the force-limited relative rotation can occur completely independently of the second force-limiting device at the beginning of the relative rotation, during the relative rotation, and at the end of the relative rotation.

[0008] According to an advantageous further development, the invention proposes that the second force-limiting device be coupled to the profile head and / or to the belt shaft, so that in a then-coupled state, the force-limited relative rotation of the belt shaft relative to the locked profile head occurs with the force-limiting participation of the second force-limiting device. It is therefore proposed that the force-limiting effect of the second force-limiting device can optionally be added to a stage of the multi-stage first force-limiting device. The number of force-limiting levels achievable by the stages of the first force-limiting device can thus be doubled by the second force-limiting device.

[0009] Multi-stage first force-limiting devices are well known in the art. For example, a two-stage first force-limiting device can comprise two torsion bars, with a switching device being provided, via which it can be switched, for example by means of a pyrotechnic drive, whether both torsion bars or only one torsion bar participates in the force-limited relative rotation of the belt shaft. Thus, two force-limiting levels can be set with the first force-limiting device. Regarding the design of a multi-stage first force-limiting device, in particular a two-stage first force-limiting device, reference is made in full to WO 2020 021 003 A1, already mentioned at the beginning.

[0010] In particular, it is proposed that a drive, for example, electronically activatable, be provided, which allows coupling of the second force-limiting device in such a way that the second force-limiting device also participates in the force-limited relative rotation of the belt shaft. In particular, it is proposed that the drive be a pyrotechnic drive, by means of which a transfer of the belt retractor from the initial state to a coupled state can be triggered, in which the second force-limiting device participates in the force-limited relative rotation in addition to the first force-limiting device.

[0011] In a preferred embodiment, the second force-limiting device comprises a wheel element, which in the initial state is rotatably mounted relative to the housing frame and rotates with the belt shaft and / or an element of the first force-limiting device. In a coupled state, however, the wheel element is blocked in its rotation. The wheel element can, for example, be a gear with teeth on its outer circumference.

[0012] In particular, it is proposed that the wheel element be lockable in its rotation by means of a clamping element. The second force-limiting device thus comprises a clamping element, which is preferably driven by the pyrotechnic drive. In the initial state, the clamping element is arranged at a distance from the wheel element, which is designed in particular as a gear. The pyrotechnic drive allows the clamping element to be moved toward the rotating wheel element, so that the teeth of the wheel element engage with the clamping element. Thus, the clamping element is initially carried along by the rotating wheel element.

[0013] In this context, it is particularly provided that a housing surrounding the wheel element has a clamping structure. The clamping structure is arranged and designed such that the clamping element carried along by the wheel element moves into or against the clamping structure, so that the clamping element engaged with the teeth of the wheel element is prevented from further movement, thus also blocking the rotation of the wheel element. For example, the clamping structure can be designed as a recess in the housing, into which the clamping element is carried along by the wheel element, wherein the clamping element in particular moves against a stop.Alternatively, it can be provided that the clamping design has a starting slope along which the clamping element is initially carried by the wheel element, wherein the starting slope displaces the clamping element and thus also the wheel element transversely to the rotation axis of the wheel element, whereby a blockage of the wheel element occurs.

[0014] It can further be provided that the second force-limiting device comprises a driver, which, in the coupled state, drives a force-limiting element and rotates with the belt shaft and / or the first force-limiting device. For example, the driver can be connected to a deformable belt serving as a force-limiting element, which, in the coupled state, is driven by the driver during the force-limited relative rotation. The force-limiting element provides the force-limiting effect of the second force-limiting device through the deformation work.

[0015] Thus, in one embodiment, a belt acting as a force-limiting element can be coupled to the driver on the one hand and to the wheel element on the other. If the wheel element is then blocked in its rotation, particularly by means of the pyrotechnic drive and the clamping element, the driver continues to rotate relative to the fixed wheel element, thereby driving and deforming the belt.

[0016] Alternatively, it can be provided that a driver, which drives a force-limiting element in the coupled state, is decoupled from the belt shaft in the initial state. In the initial state, the driver is therefore not driven by the belt shaft and / or the first force-limiting device, but is actively coupled to the belt shaft and / or the first force-limiting device. For this purpose, the driver can be coupled to the belt shaft, for example, by means of pawls, wherein the pawls are mounted in particular on a coupling ring which rotates with the belt shaft and / or the first force-limiting device and is connected to a wheel element in the initial state. For this purpose, the wheel element can, for example, have pin-like projections onto which the coupling ring with recesses is slipped.If the wheel element is blocked in its rotation, for example, by the pyrotechnically driven clamping element, the coupling ring breaks off from the wheel element, as the coupling ring is rotationally fixedly connected to the belt shaft and / or the first force-limiting device. The resulting relative rotation between the coupling ring and the wheel element causes the locking pawls to engage with locking projections on the wheel element.

[0017] The relative rotation of the coupling ring relative to the locked wheel element also engages the pawls with the driver, causing the initially stationary driver to rotate together with the coupling ring. The driver, in turn, is connected, for example, to a deformable band element, with the band element being pulled, in particular, through a baffle, thereby performing deformation work that provides the force-limiting contribution of the second force-limiting device.

[0018] In one embodiment, the second force-limiting device can be arranged between the profile head and the belt shaft. Alternatively, the second force-limiting device can be arranged on a side of the belt shaft opposite the profile head. In principle, it would also be possible to provide two second force-limiting devices, with the force-limiting devices arranged on opposite sides of the belt shaft. This allows for an ideal weight distribution of the entire belt retractor.

[0019] For a compact design of the belt retractor, it is proposed that a pyrotechnic drive of the first force-limiting device and a pyrotechnic drive of the second force-limiting device be arranged in a common housing. Alternatively, it can be provided that a pyrotechnic drive of the first force-limiting device and a pyrotechnic drive of the second force-limiting device are arranged in separate housings. In this context, it is also proposed that the belt retractor be designed for modular expansion. Depending on the application, the belt retractor can be expanded to include the second force-limiting device. For this purpose, the second force-limiting device, which has the housing for accommodating the pyrotechnic drive, can be plugged onto at least one component (for example, an element - such as a torsion bar - of the first force-limiting device and / or the belt shaft).The belt retractor is therefore modularly expandable, with the second force limiting device having connection designs that are complementary to corresponding connection designs of the rest of the belt retractor.

[0020] The invention and the technical environment are explained below using the figures as examples. They show schematically

[0021] Figure 1 : a sectional view through a belt retractor,

[0022] Figure 2: an exploded view of a first embodiment of a second force limiting device,

[0023] Figure 3 : a plan view of the second force limiting device in an initial state,

[0024] Figure 4: a plan view of the second force limiting device in a coupled state, Figure 5: an exploded view of a second embodiment of a second force limiting device,

[0025] Figure 6: a perspective view of components of the second force limiting device according to Figure 5,

[0026] Figure 7: a diagram illustrating possible force limiting levels.

[0027] The belt retractor shown in Figure 1 comprises a belt shaft 2, which is rotatably mounted in a housing frame 1. The belt shaft 2 is connected in a rotationally fixed manner to a profile head 3. To initiate a force-limited relative rotation of the belt shaft 2 with respect to the housing frame 1, the profile head 3 can be locked in a known manner so that it no longer rotates relative to the housing frame 1.

[0028] The belt retractor comprises a multi-stage first force-limiting device 4, which comprises a first torsion bar 4.1 and a second torsion bar 4.2. The multi-stage first force-limiting device 4 also comprises a known switching device, so that the force-limited relative rotation of the belt shaft 2 relative to the locked profile head 3 can occur either with both torsion bars 4.1 and 4.2 or with only one of the torsion bars.

[0029] The belt retractor also includes a second force limiting device 5.

[0030] A first embodiment of a second force-limiting device 5 is shown in Figures 2 to 4. The second force-limiting device comprises a wheel element 5.3 having external teeth, a driver 5.4, a force-limiting element 5.5 designed as a band, and a clamping element 5.2, which can be driven by a pyrotechnic drive 5.1 (see in particular Figure 3). The pyrotechnic drive 5.1 of the second force-limiting device 5 is arranged in a common housing 6, in which a pyrotechnic drive for the switching device of the first force-limiting device 4 is also arranged. Alternatively, the pyrotechnic drives can also be arranged in separate housings, thereby enabling a modular design.

[0031] The driver 5.4 is non-rotatably connected to the second torsion bar 4.2 of the first force-limiting device. In the initial state, the wheel element 5.3 rotates due to the connection to the driver 5.4 via the belt 5.5.

[0032] If the pyrotechnic drive 5.1 is now triggered, the clamping element 5.2, which in the initial state is spaced apart from the gears of the wheel element 5.3 (see in particular Figure 3), is pressed onto the wheel element 5.3 (see Figure 4). The teeth of the wheel element 5.3 engage with the clamping element 5.2. Since the clamping element 5.2 cannot follow the rotational movement due to its contact with the housing, the wheel element 5.3 is blocked. This subsequently causes the driver 5.4 to rotate relative to the blocked wheel element 5.3, deforming the force-limiting element 5.5. In this way, an additional force-limiting level is provided by the second force-limiting device 5.

[0033] The embodiment shown in Figure 5 comprises a chicane 5.8 through which a band 5.5 designed as a force limiting element can be pulled. The band 5.5 is connected to a driver 5.4 which, in the initial state, does not rotate with the belt shaft 2 and / or the first force limiting device 4. The second force limiting device in Figure 5 also has a coupling ring 5.7 and pawls 5.6. In an initial state, the coupling ring 5.7 is connected in a rotationally fixed manner to the wheel element 5.3. For this purpose, the coupling ring 5.7 is placed on pins 5.3.1 on the wheel element 5.3 (see Figure 6). The coupling ring 5.7 is connected in a rotationally fixed manner to the second torsion bar 4.2 of the first force limiting device 4, so that in the initial state the wheel element 5.3 rotates together with the coupling ring 5.7.

[0034] If the wheel element 5.3 is now blocked by the clamping element 5.2 (similar to the embodiment in Figure 2), the pins 5.3.1 break off the wheel element 5.3, and the coupling ring 5.7 continues to rotate relative to the blocked wheel element 5.3. This relative movement causes the locking pawls 5.6 to engage with projections 5.3.2 on the wheel element 5.3. In this state, the locking pawls 5.6 protrude beyond the outer circumference of the coupling ring 5.7 and engage in a form-fitting design on the inside of the driver 5.4. In this state, the driver 5.4 rotates with the coupling ring 5.6 (5.7), whereby the belt 5.5 is pulled through the chicane 5.8. In this state, a force-limited relative rotation of the belt shaft occurs with the participation of the second force-limiting device 5.

[0035] Figure 7 schematically shows, by way of example, four force limiting levels 7.1, 7.2, 7.3, and 7.4, which can be adjusted using a belt retractor according to the invention. The first force limiting level 7.1 can be adjusted by means of the multi-stage first force limiting device 4, in that both torsion bars 4.1 and 4.2 participate in the force-limited relative rotation. If one of the torsion bars 4.1 or 4.2 is decoupled by means of a switching device, the second force limiting level 7.2 is achieved. If the second force limiting device 5 is coupled, the two force limiting levels achievable by the first force limiting device 4 can be increased, so that the third force limiting level 7.3 and the fourth force limiting level 7.4 can be adjusted. During the force-limited relative rotation of the third force limiting level 7.3, both torsion bars 4.1 and 4.2 of the first force-limiting device 4 and the second force-limiting device 5 are involved, while the force-limited relative rotation of the fourth force-limiting level 7.4 involves one of the two torsion bars 4.1 or 4.2 of the first force-limiting device 4 and the second force-limiting device 5. The four force-limiting levels can be set staggered in time or at the beginning of the relative rotation.

[0036] List of reference symbols Housing frame Belt shaft Profile head First force limiting device First torsion bar Second torsion bar Second force limiting device Pyrotechnic drive Clamping element Wheel element Pin Projection Driver Force limiting element Locking pawl Coupling ring Baffle Housing First force limiting level Second force limiting level Third force limiting level Fourth force limiting level

Claims

Claims: Belt retractor for a motor vehicle seat belt, comprising a belt shaft (2) rotatably mounted in a housing frame (1), a profile head (3) lockable relative to the housing frame (1), a multi-stage first force limiting device (4), wherein the first force limiting device (4) is coupleable on one side with the profile head (3) and on the other side with the belt shaft (2), and wherein the first force limiting device (4) enables a force-limited relative rotation of the belt shaft (2) relative to the locked profile head (3), and at least a second force limiting device (5), characterized in that in an initial state the second force limiting device (5) is decoupled, so that the force-limited relative rotation of the belt shaft (2) relative to the locked profile head (3) takes place without force-limited participation of the second force limiting device (5).A seatbelt retractor according to claim 1, wherein the second force limiting device (5) can be coupled to the profile head (3) and to the belt shaft (2) such that, in a coupled state, the force-limited relative rotation of the belt shaft (2) relative to the locked profile head (3) occurs with force-limited participation of the second force limiting device (5). A seatbelt retractor according to claim 1 or 2, wherein the second force limiting device (5) comprises a pyrotechnic drive (5.1). comprising a device by which the belt retractor can be switched from its initial state to a coupled state. Belt retractor according to any of the preceding claims, wherein the second force limiting device (5) comprises a clamping element (5.2), which is in particular pyrotechnically actuated. Belt retractor according to any of the preceding claims, wherein the second force limiting device (5) comprises a wheel element (5.3) which is rotatably mounted relative to the housing frame (1) in the initial state and which is blocked in its rotation in a coupled state. Belt retractor according to any of the preceding claims, wherein a driver (5.4), which drives a force limiting element in the coupled state, rotates with the belt shaft (2) and / or the first force limiting device (4) in the initial state. Belt retractor according to any of claims 1 to 5, wherein a driver (5.4), which in the coupled state is a force limiting element (5.5) is decoupled from the belt shaft (2) in the initial state. Belt retractor according to claim 7, wherein the driver (5.4) can be coupled to the belt shaft (2) by means of pawls (5.6), wherein the pawls (5.6) are in particular mounted on a coupling ring (5.7) which rotates with the belt shaft (2) and is connected to a wheel element (5.3) in the initial state. A seatbelt retractor according to any of the preceding claims, wherein the second force-limiting device (5) is arranged between the profile head (3) and the belt shaft (2) or on a side of the belt shaft (2) opposite the profile head (3). A seatbelt retractor according to any of the preceding claims, wherein the second force-limiting device (5) comprises at least one belt that deforms during force limitation as a force-limiting element (5.5). A seatbelt retractor according to any of the preceding claims, wherein a pyrotechnic drive of the first force-limiting device and a pyrotechnic drive of the second force-limiting device are arranged in separate housings (6).

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