Pressure unit and end fitting having a pressure unit of this type

The invention relates to a pressure unit (64) for pressurizing a belt shaft (12) in a seat belt system comprising a screw (66) for fastening the pressure unit (64) to a frame (18) of the seat belt system, the screw (66) including a screw head (68) and a screw shank (70), wherein the pressure unit (64) comprises a fastening portion (72) having a screw hole (74) for inserting the screw shank (70), wherein radial play is provided between the screw hole (74) and the screw shank (70) and the fastening portion (72) on the screw head side includes mounting arms (76) for axially fixing the screw (66) in a pre-assembly position. Moreover, the invention also comprises an end fitting (11) of a seat belt system comprising such pressure unit (64).

RELATED APPLICATIONS

This application corresponds to PCT/EP2015/001304, filed Jun. 29, 2015, which claims the benefit of EP Application No. 14002281.5, filed Jul. 3, 2014, the subject matter, of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

The invention relates to a pressure unit for pressurizing a belt shaft in a seat belt system comprising a screw for fastening the pressure unit to a frame of the seat belt system, wherein the screw includes a screw head and a screw shank and wherein the pressure unit comprises a fastening portion having a screw hole for inserting the screw shank. Further, the invention relates to an end fitting comprising said pressure unit, with a tensioner drive being preferably provided which is adapted to drive the belt shaft in a winding direction.

Belt tensioners for seat belt systems are generally known from automotive engineering. In so called end fitting tensioners in the case of activation of the belt tensioner the actually fixed end of webbing usually connected to the seat frame or the vehicle body is tightened to provide for tensioning of the entire webbing. In prior art both linearly operating and rotational end fitting tensioners are described. In the case of the rotational end fitting tensioners the webbing end is connected to a belt shaft which is driven upon activation of the belt tensioner so as to wind webbing onto the belt shaft.

For mounting the seat belt system especially with reference to end fitting tensioners increasingly there is wanted a process in which the webbing end is not fastened to the belt tensioner before the belt tensioner has been mounted on the vehicle body or on the seat frame.

In order to enable such subsequent fastening of the webbing with minimum assembly effort, DE 10 2011 117 052 A1 suggests an end fitting tensioner for a seat belt system comprising a frame, a belt shaft being rotatably supported in the frame about an axis as well as a belt shaft insertion element to which one end of webbing is fastened, wherein the belt shaft includes a recess for receiving the belt shaft insertion element and wherein the belt shaft insertion element can be inserted substantially radially into the recess. Moreover, there is provided a generic pressure unit which in the completely mounted state of the end fitting pressurizes the belt shaft into its locking position and thus ensures high functional safety of the end fitting tensioner.

SUMMARY OF THE INVENTION

It is the object of the invention to provide a pressure unit which is easy to manufacture and inexpensive and which can be permanently and reliably fastened to the frame of an end fitting with minimum assembly effort.

This object is achieved, according to the invention, by a pressure unit of the type as described in the beginning in which radial play is provided between the screw hole and the screw shank and on the screw head side the fastening portion includes mounting arms for axially fixing the screw in a pre-assembly position. This results in an advantageous subassembly of the pressure element and the screw, the screw being pre-assembled on the fastening portion of the pressure unit.

In an embodiment the fastening portion includes a first frame-side contact surface and an axially opposed second screw head-side contact surface, with the end of the screw facing away from the screw head being arranged in the pre-assembly position axially between a free end of the mounting arms and the first contact surface of the fastening portion. Accordingly, the screw forms a pre-assembled subassembly together with the pressure unit, but it does not project from the frame-side contact surface of the fastening portion so that the pressure unit can be easily positioned relative to the frame of the end fitting.

In a further embodiment the screw is a collar screw having a screw collar in the axial direction between the screw head and the screw shank, with the diameter of the screw collar being between the diameter of the screw shank and the diameter of the screw head. The screw collar thus forms a stop when the screw is screwed into the frame of the end fitting and consequently in a simple manner defines a desired distance between the screw head and the frame.

Preferably in this embodiment a minimum dimension of the screw hole perpendicularly to the shank axis of the screw is larger than the diameter of the screw collar and smaller than the diameter of the screw head. Thus an edge of the screw hole forms a stop for the screw head, whereas the screw collar can be received in the screw hole.

Furthermore, the thickness of the fastening portion at the edge of the screw hole may be slightly larger than the length of the screw collar. Slightly larger in this context means in particular that the thickness of the fastening portion is larger than the length of the screw collar by at most 1 mm, preferably by at most 0.5 mm. If the material of the fastening portion exhibits certain deformability, the pressure unit thus can be fastened to the frame with a defined bias.

Of preference, the screw collar includes a groove peripheral in the circumferential direction, with the mounting arms of the pressure unit engaging in said groove in the pre-assembly position of the screw. In this way, the screw can be axially fixed in the pre-assembly position relative to the pressure unit with minimum effort.

In another embodiment of the pressure unit the mounting arms are radially elastic spring arms, especially two opposed radially elastic spring arms loading the screw radially inwardly in the pre-assembly position.

Preferably, the mounting arms include inclined surfaces facing the screw head on which, when axially loaded, the screw head is adapted to slide in the direction of the first frame-side contact surface, wherein the spring arms will deform radially outwardly.

In another embodiment the pressure unit comprises a plastic member formed integrally with the fastening portion. For example, the plastic member is a simple injection-molded part and thus allows especially low-cost manufacture of the pressure unit.

Furthermore, the pressure unit preferably comprises at feast one spring element for loading the belt shaft of the seat belt system, wherein said at least one spring element may be partly surrounded by injection molding with plastic material of the plastic member in the form of an injection-molded pad.

For the rest, the technical object is also achieved by an end fitting of a seat belt system comprising an afore-mentioned pressure unit, a frame made from metal and having a threaded hole for fastening the pressure unit to the frame and a belt shaft which is rotatably supported in the frame about an axis, wherein the screw extends, in a fastening position, with radial play through the screw hole of the pressure unit and is screwed into the threaded hole of the frame.

The screw preferably is a collar screw and in the axial direction between the screw head and the screw shank includes a screw collar, with the diameter of the screw collar being between the diameter of the screw shank and the diameter of the screw head, wherein the screw head on the collar side has a contact surface for the fastening portion and the screw collar on the shank side has a contact surface for the frame.

Especially preferred, the thickness of the fastening portion is slightly larger than the length of the screw collar, wherein in the fastening position of the screw the contact surface of the screw head contacts the fastening portion and the contact surface of the screw collar contacts the frame. Slightly larger in this context means in particular that the thickness of the fastening portion is larger than the length of the screw collar by at most 1 mm, preferably by at most 0.5 mm. Screwing the screw up to a metal/metal contact between the contact surface of the screw collar and the frame will permanently result in a defined and reliable fastening of the pressure unit on the frame of the end fitting, while the fastening portion is biased. The fastening is especially independent of the materiel of the fastening portion. This is of particular advantage with a preferred manufacture of the fastening portion of plastic material, because the material behavior of the plastic material which can hardly be estimated over time (creep, ageing) thus will not affect the connection between the pressure unit and the frame.

DESCRIPTION

FIGS. 1 to 4illustrate an end fitting tensioner10for a seat belt system in an automotive vehicle, comprising an end fitting11and a tensioner drive40. The end fitting11comprises a belt shaft12to which one end14of webbing16is fixed and a frame18made from metal and being adapted to be fixedly mounted to the vehicle body in which frame the belt shaft12is supported, wherein upon activation of the end fitting tensioner10the belt shaft12can be rotated relative to the frame18in a winding direction of the webbing so as to wind up webbing16.

In the illustrated embodiment the end14of the webbing16is stitched to form an eye enclosing a belt shall insertion element20, with the belt shaft insertion element20being received in a recess22of the belt shaft12and being supported relative to the belt shaft12in a rotationally fixed manner.

According toFIG. 2, the frame18of the end fitting tensioner10is U-shaped and comprises a land24as well as two opposed legs28,28, each leg26,28having an opening30,32through which the belt shaft12extends. Furthermore, a fastening tab33bent from the land24is provided by which the frame18can be tightly connected, especially screwed to a vehicle seat or a vehicle body.

The belt shaft12is rotatably supported about an axis A within the frame18. At the axial ends of the belt shaft12a cap34and, resp., a rope reel36are arranged, the cap34and the rope reel36being tightly connected to, especially press-fitted with the belt shaft12and prevent axial movement of the belt shaft12relative to the frame18or minimize said movement to little axial play.

For tightening the webbing16upon activation of the end fitting tensioner10a power transmission element38coupling the belt shaft12to a tensioner drive40is provided. The power transmission element36in the illustrated embodiment is a pull rope41which is partly wound onto the rope reel36and is fastened by one rope end to the rope reel36.

The tensioner drive40of the end fitting tensioner10comprises a tensioner tube42for receiving and guiding a pressurizing element44as well as a separate generator housing46for accommodating a gas generator48. The generator housing46in the shown embodiment is a tubular piece so that both the tensioner tube42and the generator housing46are made from a metal tube, especially a steel tube. Moreover, there is provided a coupling element50tightly connecting the generator housing46to the tensioner tube42(cf.FIG. 1).

According toFIG. 1, the pressurizing element44is a piston which is substantially sealed in the bent tensioner tube42and is accommodated movably along a tubular axis. The pull rope41fastened by one rope and to the rope reel36extends from the rope reel36into the tensioner tube42and is fastened there to the piston by an opposite rope end. Upon activation of the gas generator48, gas pressure is applied to the piston which moves in the direction of a free tube end52of the tensioner tube42. Accordingly, while rotating the belt shaft12pull rope41is unwound from the rope real36and at the same time webbing16is wound onto the belt shaft12so that the belt is tensioned.

For the rest, a stabilizing unit54is provided to reinforce the connection between the tensioner tube42and the generator housing46and to provide a simple connection between the tensioner drive40and the frame18. Said stabilizing unit54in the present case comprises two stabilizing elements55, especially made from zinc die casting, and a connecting element58e.g. in the form of a tubular rivet (cf.FIGS. 3 and 4).

As a matter of course, the end fitting tensioner10according toFIGS. 1 to 4may also be driven by a hydraulic motor or may be equipped with a different alternative tensioner drive, especially a so called “power snake” drive. “Power snake” in this context denotes a flexible elastically and/or plastically deformable plastic element which is received to be largely sealed and guided to be longitudinally displaceable in the tensioner tube42.

FIGS. 5 to 8illustrate the process of subsequent assembly of the webbing16on the end fitting11of the afore-described end fitting tensioner10which was tightly installed already in advance on a seat frame or a body of the vehicle.

According toFIG. 5, the belt shaft insertion element20including webbing16fixed thereto is supplied to the already installed part of the end fitting11, until bearing portions58of the belt shaft insertion element20are located radially outside the fork bearings60formed in the belt shaft12(cf.FIG. 6).

As indicated inFIG. 6by an arrow62, the belt shaft insertion element20can then be inserted by radial movement relative to the belt shaft12into the recess22and the fork bearings60so that the belt shaft insertion element20is connected to the belt shaft12in a rotationally fixed manner (cf.FIG. 7).

In order to prevent the belt shaft insertion element20and the webbing16fastened thereto from inadvertently loosening from the belt shaft12, according toFIG. 7a pressure unit64′ is inserted between the belt shaft12and the land24of the frame18and is fixed on the frame18(cf.FIG. 8). The pressure unit64′ is preferably designed so that it can be inserted only when the belt shaft insertion element20is correctly mounted on the belt shaft12so as to exclude incorrect mounting of the belt shaft insertion element20on the belt shaft12.

While in theFIGS. 1 to 8the end fitting11of the end fitting tensioner10including a conventional pressure unit64′ is illustrated, in theFIGS. 9 to 14a pressure unit64according to the invention is shown which is adapted to replace the conventional pressure unit64′ without the residual end fitting11having to be constructively modified.

TheFIGS. 9 to 11show the pressure unit64for pressurizing the belt shaft12of the end fitting11comprising a screw66for fastening the pressure unit64to the frame18of the end fitting11, wherein the screw66includes a screw head68and a screw shank70having a shank axis A. The pressure unit64accordingly comprises a fastening portion72having a screw hole74for inserting the screw shank70, wherein radial play is provided between the screw hole74and the screw shank70, and wherein the fastening portion72includes mounting arms76on the screw head side for axially fixing the screw66in a pre-assembly position according toFIG. 9.

In the shown embodiment the pressure unit64comprises a plastic member78formed integrally with the fastening portion72of the pressure unit64. Apart from the plastic member78, the pressure unit64moreover includes two spring elements80for loading the belt shaft12of the seat belt system into its looking position.

In particular, the two spring elements80are partly surrounded by injection molding with plastic material of the plastic member78in the form of an injection-molded part so that the pressure unit64may be easily and inexpensively manufactured and may be geometrically adapted to different end fittings11with minimum effort.

According toFIG. 11, the fastening portion72of the pressure unit64includes a first frame-side contact surface82and an axially opposed second contact surface84on the screw head side, wherein the end86of the screw66facing away from the screw head68in the pre-assembly position is arranged axially between a free end88of the mounting arms76and the first contact surface82of the fastening portion72.

In addition, it becomes evident fromFIG. 11that the screw66is a collar screw and in the axial direction between the screw head68and the screw shank70has a screw collar90, with the diameter d of the screw collar90being larger than the diameter of the screw shank70and being smaller than the diameter of the screw head68.

Furthermore, according toFIG. 10a minimum dimension Sminof the screw hole74perpendicularly to the shank axis A is larger than the diameter d of the screw collar90and smaller than the diameter of the screw head68. Consequently, an edge of the screw hole74forms a stop for the screw head68, whereas the screw collar90may be received in the screw hole74.

In the axial direction the thickness t of the fastening portion72at the edge of the screw hole74is slightly larger than the length l of the screw collar90. Hence the pressure unit64can be fixed on the frame18of the end fitting11with a defined bias while deforming the plastic material of the fastening portion72.

According toFIG. 11, the screw collar90includes a groove92peripheral in the circumferential direction, wherein the mounting arms76of the pressure unit64engage in said groove92in the shown pre-assembly position of the screw66. In the present embodiment, the mounting arms76are two opposed radially elastic spring arms which radially inwardly load the screw66in its pre-assembly position.

The mounting arms76for the rest include inclined surfaces94facing the screw head68, with the screw head68being adapted to slide along said inclined surfaces when it is axially loaded in the direction of the frame-side contact surface82.

In its pre-assembly position according toFIGS. 9 to 11the screw66is captively connected to the fastening portion72of the pressure unit64and together with the pressure unit64forms a pre-assembled subassembly adapted to be easily and reliably mounted, for example on an end fitting11according toFIG. 6.

The end fitting11of the seat belt system for automotive vehicles then comprises the pressure unit64according toFIGS. 9 to 11, the frame18made from metal and having a threaded hole96for fastening the pressure unit64and the belt shaft12which is rotatably supported in the frame18about a belt shaft axis, wherein the screw66extends through the screw hole74of the pressure unit64with radial play in its final assembly or fastening position (cf.FIG. 15) relative to the shank axis A and is screwed into the threaded hole96of the frame18.

FIGS. 12 and 13illustrate detailed sections of the pressure unit64in the area of the fastening portion72, wherein according toFIG. 12the screw66is pre-assembled on the fastening portion72and according toFIG. 13is in its pre-assembly position.

FIGS. 14 and 15illustrate detail cutouts of the end fitting11in the area of the fastening portion72, wherein the pressure unit64according toFIG. 14is mounted on the frame18of the end fitting by means of the screw66and wherein the screw66is provided in its final mounting or fastening position according toFIG. 15.

According toFIG. 12, the screw66is initially pressed into the screw hole74of the fastening portion72, wherein the elastic mounting arms76are deformed radially outwardly by the screw collar90and upon reaching the groove92of the screw collar90snap radially inwardly and engage in the groove92. In said pre-assembly position of the screw66according toFIG. 13the pressure unit64forms a pre-assembled subassembly with the screw66.

The pressure unit64will then be delivered as pre-assembled subassembly according toFIG. 13and in the following is mounted on the frame18of the end fitting11fastened already on the vehicle body side. After positioning the pre-assembled subassembly relative to the frame18, according toFIG. 14the screw66is further pressed into the threaded hole96of the frame18, until a male thread102of the screw shank70acts on a female thread104of the threaded hole. Accordingly, the mounting arms76are deformed radially outwardly by the screw head68. Finally the screw66is screwed into the threaded hole96of the frame18, until it reaches its final assembly or fastening position according toFIG. 15, with the mounting arms76snapping radially inwardly on the side of the screw head68facing away from the screw collar90.

The screw head68includes on the collar side a contact surface98for the fastening portion72and the screw collar90includes on the shank side a contact surface100for the frame18, wherein in the fastening position of the screw66according toFIG. 15the contact surface98of the screw head63contacts the fastening portion72and the contact surface100of the screw collar90contacts the frame18. In other words, this means that the screw66is screwed up to a metal/metal contact between the contact surface100of the screw collar90and the frame18, which permanently results in a defined and reliable fastening of the pressure unit64on the frame18of the end fitting11while the fastening portion72is biased. The fastening is especially independent of the plastic material of the fastening portion72whose long-term behavior in terms of creep and ageing effects can hardly be estimated.

In the present embodiment, the pressure unit64is configured so that the mounting arms76slide radially outwardly on the screw head68, when the pressure unit64is removed from the frame18, i.e. when the screw66is unscrewed. In this way, the screw66can be easily moved via the position according toFIG. 14into its pre-assembly position according toFIG. 13again and allows re-using the pressure unit64.

If re-use of the pressure unit64is not desired, for example for safety reasons, the screw head68and/or the mounting arms76may be configured so as to impede or prevent non-destructive removal of the pressure unit64.