Belt penalty

Abstract

A belt tensioner (10) for a safety belt system, comprising a tensioning tube (20) with an open outlet end and a force transmission element (22) guided in the tensioning tube (20) and exiting the tensioning tube (20) via the open outlet end, a gas generator (18) providing compressed gas for displacing the force transmission element (22) in the tensioning tube (20), and a drive wheel (16) set in rotation by the force transmission element (22) exiting the tensioning tube (20), wherein a guide component (24) surrounding the drive wheel (16) is provided, into which the force transmission element (22) enters as soon as it exits the tensioning tube (20), and an energy-dissipating structure (50) is provided on the guide component (24), with which the force transmission element (22) comes into contact when it has at least substantially completely exited the tensioning tube (20), characterized in thatthat the energy-dissipating structure (50) comprises at least one cutting edge (52) for engagement with the force transmission element (22).

Description

[0001] The invention relates to a pyrotechnically driven belt tensioner for a safety belt system.

[0002] A belt pretensioner is designed to reduce certain factors that could negatively impact the restraint of a vehicle occupant in a restraint situation, before the vehicle occupant is displaced forward and, if necessary, a force limiting device is activated. These factors include the so-called slack-in effect (belt webbing wound loosely onto the belt reel) and slack-in effect (belt webbing lying loosely against the vehicle occupant). The belt pretensioner reduces slack and the slack-in effect within a very short time, for example, by winding belt webbing onto a belt reel of a belt retractor, thereby tightening the belt webbing. This allows the vehicle occupant to participate in the vehicle's deceleration at an early stage. It also improves the conditions for the subsequent deployment of a force limiting device.

[0003] Nowadays, pyrotechnically driven belt tensioners are commonly used to provide the high forces required for belt tensioning in a sufficiently short time.

[0004] In a known design of a belt pretensioner, a force transmission element is provided that is displaced in a tensioner tube by the gas pressure generated by a gas generator when the belt pretensioner is activated. The force transmission element interacts with the belt spool and causes it to rotate to tighten the belt.

[0005] From the generic DE 10 2006 031 360 A1, a belt tensioner for a safety belt system is known, which comprises a tensioner tube with an open outlet end and a force transmission element that is guided in the tensioner tube and exits the tensioner tube via the open outlet end. Furthermore, a gas generator is part of the belt tensioner, which provides compressed gas to displace the force transmission element in the tensioner tube, as well as a drive wheel set in rotation by the force transmission element exiting the tensioner tube. The force transmission element enters a guide component surrounding the drive wheel as soon as it exits the tensioner tube, wherein an energy-absorbing structure is provided on the guide component, with which the force transmission element comes into contact when it has at least substantially completely exited the tensioner tube.

[0006] Furthermore, JP 2016 037 184 A discloses a belt tensioner in which the energy dissipation element is a stopping element.

[0007] The object of the invention is to better control the movement of the force transmission element in a belt tensioner of the type mentioned above, in particular after it has driven the belt reel.

[0008] This problem is solved by the characterizing features of claim 1.

[0009] The force transmission element interacts with the drive wheel, preferably directly after leaving the tensioner tube, in a predetermined engagement area in order to transfer the highest possible kinetic energy to the belt spool. The energy-absorbing structure reduces the kinetic energy of the force transmission element in a defined, reproducible manner after it has interacted with the drive wheel and transferred part of its kinetic energy to it. The energy-absorbing structure therefore ensures that the force transmission element moves within predetermined ranges after leaving the tensioner tube and, in particular, does not re-engage with the drive wheel, so that the force level of a force limitation following belt tensioning is clearly defined.

[0010] Advantageously, the energy-absorbing structure stops the power transmission element, preferably bringing the power transmission element to a complete standstill. This occurs, for example, in an area of the circumference of the drive wheel where the power transmission element cannot come into contact with the engagement area and the drive wheel.

[0011] In order to protect the drive wheel from contact with the power transmission element outside the engagement area, the guide component according to a preferred embodiment has a radially inner circumferential wall which extends over most of the circumference of the drive wheel, in particular approximately over 200° to 270°, which surrounds the drive wheel and prevents contact of the power transmission element with the drive wheel.

[0012] The guide component can have a guide groove for the force transmission element, which is formed by the inner peripheral wall and by two sections of the guide component extending radially outward from the axial ends of the peripheral wall.

[0013] In the engagement region, which may comprise approximately 90 to 160°, the radially inner peripheral wall is preferably omitted so that the force transmission element emerging from the tensioner tube can interact with the drive wheel and drive the drive wheel.

[0014] The force transmission element can be formed as a single piece or consist of several separate parts, for example, a series of balls, which can also be coupled together if necessary. The functional principle of the belt tensioner and the advantage of an intermediate element positively coupled to the stop element are the same in all cases.

[0015] When using a one-piece force transmission element, this can, for example, be an elongated, flexible, elastic and / or plastically deformable plastic component.

[0016] In this case, in a preferred embodiment, the force transmission element has a tapered segment in the region of a rear end with a reduced diameter compared to a front segment, wherein interaction with the drive wheel is reduced when the tapered segment passes the drive wheel. The rear end is the end of the force transmission element located at the rear in the direction of movement. Thus, the tapered segment only reaches the engagement area of the drive wheel late in the belt tensioning process. By reducing interaction with the drive wheel at this time, the kinetic energy of the force transmission element remains higher, and the force transmission element moves completely out of the tensioner tube. This ensures that the drive wheel and thus the belt spool are released for subsequent force limitation.

[0017] The tapered segment can be located in front of an actual end segment of the force transmission element. This end segment is preferably divided into several, in particular two or four, parts via predetermined breaking points, which are separated from the rest of the force transmission element at the latest when they exit the tensioner tube. This feature also helps ensure that the force transmission element completely exits the tensioner tube and that the interaction of the force transmission element with the drive wheel is reduced as much as possible after the belt tensioning is completed, enabling a defined force level for the subsequent force limitation.

[0018] The energy-absorbing structure is preferably arranged as far away as possible from the open outlet end of the tensioner tube in the direction of movement of the force transmission element, so that an elongated force transmission element can completely exit the tensioner tube before it is stopped at its front end by the energy-absorbing structure.

[0019] Viewed in the direction of rotation of the drive wheel (corresponding to the direction of movement of the power transmission element), the energy-absorbing structure can, for example, be positioned at an angle of approximately 235° to 345° from the open outlet end of the tensioner tube. This corresponds approximately to the end of the normal travel of the power transmission element, at which the power transmission element has completely passed the engagement area.

[0020] The radially inner wall may end at the energy-dissipating structure, viewed in the direction of rotation of the drive wheel, while it preferably begins directly after the engagement section.

[0021] Preferably, the engagement section extends from the open outlet end of the tensioner tube not only in the direction of rotation of the drive wheel, but also by a certain distance, e.g., approximately 30 to 60°, opposite to the direction of rotation of the drive wheel. This makes it possible, at the beginning of the force limitation, during which the belt reel and thus the drive wheel rotate opposite to the direction of rotation during belt tensioning, to remove any remnants of the force transmission element still engaged with the drive wheel by rotating it in the opposite direction, without coming into disruptive contact with the radially inner circumferential wall and / or the energy-absorbing structure.

[0022] The energy-dissipating structure can, for example, be formed on a radially outer circumferential wall of the guide component, which extends only over a small portion of the outer circumference of the guide component, in particular over approximately 10 to 45°. This radially outer circumferential wall preferably comprises only the energy-dissipating structure. This circumferential wall also prevents the force transmission element from deflecting radially outward. Furthermore, the circumferential wall increases the friction between the force transmission element and the guide component, which also contributes to energy dissipation.

[0023] According to the invention, the energy-dissipating structure comprises at least one cutting edge for engaging the force-transmitting element. The cutting edge digs into the force-transmitting element when it collides with the energy-dissipating structure, thus simultaneously dissipating kinetic energy and holding the force-transmitting element to the energy-dissipating structure.

[0024] The energy-dissipating structure can, for example, comprise two V-shaped cutting edges, with the V opening opposite to the direction of movement of the power transmission element. A front end of the power transmission element is thus pushed into the energy-dissipating structure, reliably preventing further movement beyond the energy-dissipating structure into renewed contact with the drive wheel.

[0025] The energy-dissipating structure may also comprise a web extending parallel to an axis of the drive wheel and connecting, in particular, the two cutting edges. This web is then preferably part of the radially outer peripheral wall.

[0026] The part of the engagement section located at the rear in the direction of rotation preferably begins directly adjacent to the energy-dissipating structure.

[0027] In this way, the power transmission element is given the longest possible travel path, which makes it possible to provide the maximum possible length for the power transmission element in the case of a one-piece power transmission element.

[0028] The guide component can be open in sections along its outer circumference, preferably except, for example, for the radially outer peripheral wall. This design allows detached parts of the force transmission element to escape the guide component. These are collected in the belt retractor frame away from the drive wheel, thus freeing up the space around the drive wheel.

[0029] The invention is described in more detail below using an exemplary embodiment with reference to the accompanying drawings. The figures show: - Fig. 1 a schematic perspective view of a belt tensioner according to the invention, integrated into a belt retractor; - Fig. 2 a guide component of the belt retractor according to the invention Fig. 1 in perspective view; - Fig. 3 a schematic representation of components of the belt retractor and the belt tensioner from Fig. 1, before the power transmission element leaves the tensioner tube; - Fig. 4 to 6 schematic perspective views of the assembly from Fig. 3 before, during and after the guide component has left the tensioner tube; - Fig. 7 a schematic perspective view of the assembly from Fig. 3, after the force transmission element has left the tensioner tube; and - Fig. 8 a schematic perspective view of a force transmission element of the belt tensioner according to the invention.

[0030] The figures show the essential parts of a belt retractor with a pyrotechnically driven belt tensioner 10 integrated therein. A belt reel 14 is rotatably mounted in a reel frame 12 of the belt retractor, onto which the belt webbing can be wound or removed (not shown here). At one end of the axis of the belt reel 14, in Fig. 1 at the left-hand end, a drive wheel 16 is provided (indicated by dashed lines in Fig. 1), which is arranged concentrically with the axis of the belt reel 14 and which is Fig. 1 is covered by a cover 17 of the belt tensioner 10. The drive wheel 16 has external teeth and serves to rotate the belt spool 14 via the belt tensioner 10.

[0031] The belt tensioner 10 has a gas generator 18, which is arranged at one end of a tensioner tube 20, so that generated compressed gas can flow into the tensioner tube 20. A force transmission element 22 is slidably arranged in the tensioner tube 20 (see also Fig. 8), which is essentially accelerated by the gas generated by the gas generator 18, exits the tensioner tube 20 through an open outlet end of the tensioner tube 20, and interacts with the drive gear 16 in an engagement region 26, so that the drive gear 16 is set in rotation by the force transmission element 22 being pushed past it. In the engagement region 26, the external toothing of the drive gear 16 is accessible to the force transmission element 22 exiting the tensioner tube 20.

[0032] The engagement area 26 is located directly at the open outlet end of the tensioner tube 20, so that the force transmission element 22 hits the drive wheel 16 with the highest possible kinetic energy (see Fig. 5).

[0033] The belt tensioner 10 also has a force limiting device, which is not shown in detail here.

[0034] The direction of movement B of the force transmission element 22 is initially determined by the shape of the tensioner tube 20 and subsequently largely by a guide component 24, discussed in more detail later, which is arranged under the cover 17 of the belt tensioner 10. The tensioner tube 20 is partially strongly curved in several spatial directions, so that the direction of movement of the force transmission element 22 is not linear.

[0035] The force transmission element 22 has a front end 28 and a rear end 30, seen in the direction of movement.

[0036] Fig. 8 shows a possible design of the force transmission element 22.

[0037] The power transmission element 22 is here a one-piece, elongated component made entirely of a plastic material that is flexible enough to follow the curvature of the tensioner tube 20 and is preferably plastically deformable enough for the drive wheel 16 to press into the power transmission element 22 and thus create an engagement structure that helps to establish good power transmission between the power transmission element 22 and the drive wheel 16 while the power transmission element 22 is pushed past the drive wheel 16.

[0038] In this example, the force-transmitting element 22 is divided into several segments. A front segment 32 extends from the front end 28 to the beginning of a tapered segment 34, which has a reduced diameter compared to the front segment 32.

[0039] The front segment 32 can be further subdivided by one or more constrictions 36 in which the diameter is reduced over a short distance.

[0040] The tapered segment 34 is followed by an end segment 38 which here has a larger diameter than the front segment 32, but the diameter is still selected such that the force transmission element 22 can slide in the tensioner tube 20 without great friction losses.

[0041] The end segment 38 is divided into four sections by constrictions 36 parallel to the direction of movement. The material of the end segment 38 can also be completely severed in these constrictions.

[0042] All constrictions 36 represent predetermined breaking points at which the power transmission element 22 can break apart after passing the drive wheel 16. In the case of the constrictions 36 in the end segment 38, this can also occur upon leaving the tensioner tube 20, whereby the end segment 38 does not necessarily have to contribute to the power transmission to the drive wheel 16.

[0043] By dividing the elongated force transmission element 22 into shorter segments, the individual sections of the force transmission element 22 can move more easily away from the drive wheel 16 after they have passed it and can accumulate in an area of the retractor frame 12 remote from the drive wheel 16, where they do not hinder rotation of the drive wheel 16 during force limitation following belt tensioning.

[0044] The tapered segment 34 contributes to the force transmission element 22 moving completely past the drive wheel 16. Since this segment is arranged near the rear end 30, it only reaches the drive wheel 16 late in the belt tensioning process, when a large part of the force transmission element 22 has already left the tensioner tube 20. By reducing the diameter, lower forces act between the force transmission element 22 and the drive wheel 16 than in the area of the front segment 32, so that the kinetic energy of the force transmission element 22 is reduced to a lesser extent. As a result, it is ensured that the force transmission element 22, when used as intended, moves further past the drive wheel 16 in the direction of movement, thus moving away from it and releasing the drive wheel before force limitation begins.

[0045] The guide component 24 surrounds the drive wheel 16 and is arranged below the cover 17. The guide component 24 is separately in Fig. 2. In this example, the guide component 24 is a one-piece plastic component that is mounted on the drive wheel 16 with a central recess so that the drive wheel 16 can rotate therein. The guide component 24 is firmly connected to the retractor frame 12 and does not rotate together with the drive wheel 16 or the belt spool 14.

[0046] Fig. 3 shows the assembly of Fig. 1 without the cover 17, so that the guide component 24 can be seen.

[0047] The guide component 24 has a radially inner circumferential wall 42 arranged concentrically around the drive wheel 16, which in this example extends completely closed over a large part of the circumference of the drive wheel 16. The radially inner circumferential wall 42 leaves only the engagement area 26 open (in Fig. 2 on the rear side of the guide component 24, not shown).

[0048] The radially inner peripheral wall 42 can, in particular, extend over an angular range of approximately 200° to 270°. Thus, an opening remains in the radially inner peripheral wall 42 over approximately 90 to 160°, in which the external toothing of the drive gear 16 is exposed and thus accessible from the outside.

[0049] The radially inner peripheral wall 42 also defines a guide groove 44, together with two radially outwardly projecting and closed circumferential portions 46, 48 of the guide component 24 from the axial ends of the peripheral wall 42. The guide groove 44 helps to keep the power transmission element 22 in the plane of the drive wheel 16.

[0050] In addition, an energy-dissipating structure 50 is provided on the guide component 24. This serves to dissipate the kinetic energy of the force-transmitting element 22 and bring it to a standstill when it comes into contact with the energy-dissipating structure 50.

[0051] For this purpose, the energy-absorbing structure in this example has two cutting edges 52, each of which runs obliquely so that they form a V open opposite to the direction of movement B of the force transmission element 22 (see the arrow in Fig. 2). Viewed in the direction of movement B, the two cutting edges 52 are connected by a web 54 which extends parallel to an axis of the drive wheel 16 and which, together with the radially inner peripheral wall 42 and the upper and lower radially projecting portions 46, 48, forms a passage into which the front end 28 of the power transmission element 22 enters.

[0052] The direction of movement B of the force transmission element 22 coincides with the direction of rotation of the drive wheel 16 during belt tensioning.

[0053] The entire energy-dissipating structure 50 here forms a radially outer peripheral wall 56, which, however, extends only over a very narrow angular range. For example, the radially outer peripheral wall 56 occupies approximately 10 to 45° along the outer circumference of the guide component 24, including the cutting edges 52.

[0054] With the exception of this radially outer circumferential wall 56, the guide component 24 is essentially open over its outer circumference, in particular in the region in which the force transmission element 22 moves from the open outlet end of the tensioner tube 20 to the energy-absorbing structure 50.

[0055] The energy-absorbing structure 50 is arranged at an angle of approximately 235° to 345° from the open outlet end of the tensioner tube 20 in this example to ensure the longest possible travel path of the force transmission element 22.

[0056] The engagement region 26 also extends counter to the direction of movement B of the force transmission element 22 from the open outlet end of the tensioner tube 20 over a certain angular section in which the external toothing of the drive wheel 16 is exposed to the outside, since the radially inner circumferential wall 42 is interrupted in this angular section.

[0057] When the belt tensioner 10 is activated, the gas generator 18 is ignited, and the force transmission element 22, which at this point is still completely contained in the tensioner tube 20, is accelerated. With high kinetic energy, the force transmission element 22 leaves the tensioner tube at its open exit end and strikes the external toothing of the drive wheel 16 in the engagement area 26. Here, a portion of the kinetic energy of the force transmission element 22 is transferred to the drive wheel 16 and thus the belt spool 14, causing the drive wheel 16 to rotate together with the belt spool 14.

[0058] Since the rest of the force transmission element 22 pushes from behind in the direction of movement B, the front end 28 of the force transmission element 22 moves further along the guide groove 44 of the guide component 24 away from the engagement area 26. This situation is in Fig. 5, while Fig. 4 shows the situation before belt tensioning begins.

[0059] As soon as the front end 28 of the force transmission element 22 reaches the energy-dissipating structure 50, the cutting edges 52 dig into the deformable material of the force transmission element 22 and thus dissipate its kinetic energy.

[0060] The web 54, which radially outwardly defines the guide groove 44 in this area, also helps to dissipate the kinetic energy of the force transmission element 22, slowing it down and bringing it to a standstill. The front end 28 of the force transmission element 22 slides into the gap between the radially inner circumferential wall 42 and the radially outer circumferential wall 56 or the web 54, which leads to increased friction and thus to the dissipation of kinetic energy.

[0061] The force transmission element 22 is brought to a complete stop shortly after its front end 28 has contacted the energy dissipating structure 50. This situation is shown in the Fig. 6 and Fig. 7 shown.

[0062] In this example, the radially inner peripheral wall 42 ends directly after the front end of the radially outer peripheral wall 56 in the direction of movement B. However, the force transmission element 22 is brought to a standstill and held in place by the energy-dissipating structure 50.

[0063] The end segment 38 of the power transmission element 22, which is divided here by two constrictions 26, breaks down in this example into four individual parts 38' at the latest when passing the drive wheel 16. These individual parts 38' do not always pass the drive wheel 16, but can remain in the engagement area 26 when the power transmission element 22 comes to a standstill. This is shown in Fig.7. However, as soon as a force limitation occurs, during which the drive wheel 16 is rotated counter to the direction of movement B, these individual parts 38' are pushed out of the engagement area 26. Together with any other fragments of the force transmission element 22 that were severed at the constrictions 36, these parts collect in an area of the reel frame 12 remote from the drive wheel 16, where they cannot come into contact with the drive wheel 16 again.

[0064] The energy-absorbing structure 50 is so far removed from the open outlet end of the tensioner tube 20 in the direction of movement B that the force transmission element has completely left the tensioner tube 20. It is possible that the end segment 38 has already disintegrated into its individual parts 38'.

[0065] The belt tensioner 10 was described here in connection with an elongated, flexible force transmission element 22, but it would be easily possible to transfer the inventive concept to a belt tensioner with a different force transmission element, for example, a series of individual balls or a series of individual, interconnected force transmission elements. It would also be conceivable to arrange the belt tensioner not on a belt retractor, but rather to implement it as a belt buckle or end fitting tensioner.

Claims

[1] Belt tensioner (10) for a safety belt system, comprising a tensioning tube (20) with an open outlet end and a force transmission element (22) which is guided in the tensioning tube (20) and which leaves the tensioning tube (20) via the open outlet end, a gas generator (18) which provides compressed gas for displacing the force transmission element (22) in the tensioning tube (20), and a drive wheel (16) which is set in rotation by the force transmission element (22) emerging from the tensioning tube (20), wherein a guide component (24) surrounding the drive wheel (16) is provided, into which the force transmission element (22) enters as soon as it leaves the tensioning tube (20), and an energy-dissipating structure (50) is provided on the guide component (24), with which the force transmission element (22) comes into contact when it has at least substantially completely left the tensioning tube (20), characterized bythat the energy-dissipating structure (50) comprises at least one cutting edge (52) for engagement with the force transmission element (22). [2] Belt tensioner according to claim 1, characterized by that the energy-dissipating structure (50) stops the force transmission element (22). [3] Belt tensioner according to one of the preceding claims, characterized by that the guide component (24) has a radially inner circumferential wall (42) which extends over a large part of the circumference, in particular approximately 145°, of the drive wheel (16) and surrounds the drive wheel (16). [4] Belt tensioner according to one of the preceding claims, characterized by that the force transmission element (22) is an elongated, flexible, elastically and / or plastically deformable plastic component. [5] Belt tensioner according to one of the preceding claims, characterized bythat the energy-absorbing structure (50) is arranged at an angle of approximately 245° - 280° from the open outlet end of the tensioner tube (20) when viewed in the direction of rotation (B) of the drive wheel. [6] Belt tensioner according to one of the preceding claims, characterized by that the energy-dissipating structure (50) is formed on a radially outer peripheral wall (56) of the guide component (24), which extends only over a small part of the outer circumference of the guide component (24), in particular approximately 24°. [7] Belt tensioner according to one of the preceding claims, characterized by that the energy-dissipating structure (50) comprises two V-shaped cutting edges (52), wherein the V opens counter to the direction of movement (B) of the force transmission element (22). [8] Belt tensioner according to one of the preceding claims, characterized bythat the energy-dissipating structure (50) comprises a web (54) which extends parallel to an axis of the drive wheel (16) and which in particular connects the two cutting edges (52). [9] Belt tensioner according to one of the preceding claims, characterized by that the guide component (24) is open in sections along its outer circumference.

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