GB2271270A

GB2271270A - A belt tightener for a motor vehicle safety belt

Info

Publication number: GB2271270A
Application number: GB9319214A
Authority: GB
Inventors: Martin Specht; Helmut Auernhammer
Original assignee: HS Technik und Design Technische Entwicklungen GmbH
Current assignee: HS Technik und Design Technische Entwicklungen GmbH
Priority date: 1992-09-28
Filing date: 1993-09-16
Publication date: 1994-04-13
Also published as: IT1265506B1; ITBZ930041A1; DE4232489A1; ITBZ930041A0; GB9319214D0

Abstract

A belt tightener for a safety belt of a motor vehicle comprises a prestressed compression coil spring 13 as a force storage means, for producing a drive force acting on the safety belt to tighten same. A locking means for holding the compression coil spring 13 in a prestressed condition includes a locking member 11 and a plurality of locking levers 7 disposed around the axis of the compression coil spring 13, with the axes of rotation of the locking levers 7 being arranged on a circle around the axis of the compression coil spring 13 on the locking member 11 which is moved upon release of the compression coil spring 13 by the drive force thereof. The locking levers 7 engage the locking member 11 at their one side to hold the locking member in the position in which the compression coil spring 13 is in the prestressed condition, while at their other side the locking levers 7 bear against respective abutments 25, 26. To release the drive force of the prestressed compression coil spring 13 the abutments 25, 26 which are disposed on a sensor mass body 4 are mounted movably relative to the vehicle structure upon increase acceleration or deceleration of the vehicle in the axial direction of the compression coil spring 13. <IMAGE>

Description

2271270 Belt tightener for a vehicle safety belt The invention relates to

a belt tightener for a vehicle safety belt.

A form of belt tightener for a safety belt of a motor vehicle, which can also be referred to as a belt grabber, comprises a prestressed compression coil spring acting as a force storage means to produce a drive force that acts on the safety belt to tighten it.

The c amp ression coil spring is held in the prestressed condition by a plurality of locking levers arranged around the axis of the spring, with their axes of rotation disposed on a circle around the axis of the spring on a locking member. The locking ber is awed upon release of the campression coil spring by the drive force thereof, the locking levers engaging the locking manber at their one side in the rest condition of the assembly. At their other side the locking levers bear against respective abutments, the abutments and the locking levers being movable relative to each other and the locking levers being pivotable about their axes of rotation in order thereby to release the drive force of the spring. The compression coil spring is in the form of a movable, vehicle-sensitive mass which is thus operable to release the prestressed condition thereof. When the spring is released fran its prestressed condition, the spring together with the locking levers move relative to the abutments, which are fixed with respect to the housing of the device, over a release distance so that the locking levers can pivot about their axes of rotation and release the locking manber with which they are in locking engagement.

In accordance with the present invention there is provided a belt tightener for a vehicle safety belt comprising: a compression coil spring as a force storage means for producing a drive force to act on the safety belt to tighten same; a locking mans for holding the compression coil spring in a prestressed condition, including a 2 locking member movable upon release of the ccmpression coil spring by said drive force, and a plurality of double-sided locking levers arranged around the axis of the ccmpression coil spring and having axes of rotation arranged on a circle around the axis of the ccmpression coil spring on said locking member, the locking levers engaging said locking member at their one lever side; a sensor mass body mounted movably relative to the vehicle structure by an increased acceleration or deceleration acting on the sensor mass body in the axial direction of the compression coil spring; and abutment means on the sensor mass body, the locking levers bearing with their other lever side against the abutment neans in the rest condition, the arrangeffent being such that to release the drive force of the prestressed ccmpression coil spring the abutment means and the locking levers are movable relative to each other and the locking levers are pivotable about their axes of rotation on the locking member.

In accordance with a preferred feature of the invention the sensor mass body can be so arranged that it is movable towards the axes of rotation of the locking levers. The movement of the sensor mass body can be in opposition to a sensor spring which acts in opposite relationship to the direction of the drive force produced by the compression coil spring for tightening the safety belt. In that respect the sensor spring is operative in an axial direction and is preferably arranged on the axis of the compression coil spring. That arrangement can provide that the sensor spring exerts its effect on the centre of mass of the sensor mass body.

The sensor mass body may further have openings or recesses into which the lever portions, in particular the ends, of the locking levers, which bear against the abutment means can move when the sensor mass has moved by a release distance detennined by the axial extents of the abutments and the lever aim ends bearing thereagainst. Movements of the sensor mass body which are shorter than the above- 3 mentioned release distance do not result in the locking levers being released so that under those circumstances the sensor mass body is moved back again into its starting position, wore specifically under the force of the above-mentioned sensor spring.

Both the compression coil spring and the sensor spring may be supported by way of a common carrier on the appropriate part of the vehicle structure. A roller bearing means for the sensor mass body may also be provided on the cammon carrier, thereby to ensure that the sensor mass body is movable with a low level of friction, relative to the vehicle structure. The roller bearing means can also serve for axially guiding the sensor mass body in the axial direction of the assembly.

In order to provide that the locking levers bear with the minimum level of friction against the movable sensor mass body, the sensor mass body may have first and second abutment portions for each co- operating locking lever end so that the contact pressure between the respective abutment portions and the associated locking lever at each of the abutment mans is thereby halved. For that purpose the end portion of each lever arm may be of a substantially T-shaped portion, with the limb portions which are disposed at each side of the lever arm and which extend transversely thereto resting on the first and second abutment portions in the position of co-operation between the locking lever and the respective abutment.

The contact pressure of the lever arm ends against the sensor mass body is provided by the drive force of the compression coil spring when held in the prestressed condition. In that arrangement the compression coil spring acts in the direction of the drive force on the locking levers at the lever arm thereof, which a remote from the abutment mans.

An embodiment of the invention will now be described with reference to the drawings by way of example. In the drawings:

4 Figure 1 is a side view in longitudinal section through an embodiment of a belt tightener according to the invention, Figure 2 is a plan view in the direction indicated by the arrow Z in Figure 1 in longitudinal section through the structure shown in Figure 1, Figure 3 is a view in section taken along line A-A in Figure 1, Figure 4 is a view in section taken along line B-B in Figure 1, Figure 5 is a view in section taken along line C-C in Figure Figure 6 is a view in section taken along line D-D in Figure 1, and Figure 7 is a view in section taken along line E-E in Figure 1.

In the embodiment of a belt tightener for a motor vehicle, as shown in the drawings, the essential components of the belt tightener are disposed in a housing which is in the form of a protective tube as indicated generally at 2 and which is closed at one end, being the end at the left in Figure 1, by a cover 16. A compression coil spring 13 is disposed within the housing 2 to act as a force storage means for producing the drive force for operation of the belt tightener to act on the safety belt to tighten same. The compression coil spring 13 is held in the prestressed condition shown in Figures 1 and 2 by locking levers 7. The locking levers 7 are in the form of double-sided locking levers, that is to say having first and second lever arm, and are of the configuration most clearly seen from Figure 1, for example substantially of the configuration shown in EP 0 398 010 A2. Three locking levers 7 can be arranged around the axis A of the =pression coil spring 13 at equal angular spacings of 1200.

The compression coil spring 13 is arranged around a guide tube 12. One end of the compression coil spring 13, which is the stationary end thereof, is supported against a spring plate 9. The spring plate 9 is in turn supported against a carrier 3 which is fixed to the housing structure of the belt tightener. For that purpose the carrier 3 has a bore 30 so that it can be suitably connected to an apprcpriate part of the structure of the vehicle in which the belt tightener is to be used, by weans of a screw connection (not shown).

The other end of the compression coil spring 13, which is thus at the left in Figure 1, bears against a spring anchor 14, the shape of which can also be seen in detail frcrn Figures 2 and 7. As shown in Figure 7 the spring anchor 14 has lateral anchoring surfaces 31 and 32 which are arranged on respective sides of the guide tube 12. The end of the cempression coil spring 13 is pressed against the surfaces 31 and 32. The spring anchor 14 also has a central anchoring portion 33 shown in Figure 7, which is anchored to a cable nipple 34 fixedly connected to one end of a pulling or tension cable 28. For that purpose the central anchoring portion 33 is passed through the cable nipple 34. A nipple receiving portion 15 is provided for exactly positioning the cable nipple 34 at the end of the guide tube 12. The cable receiving portion 15 may rise plastics material. The cable nipple 34 can be positively lockingly fitted into the nipple receiving portion 15, with the opening in the nipple being aligned with openings at the end of the guide tube 12. For connecting the tension cable 28 and the guide tube 12 to the spring anchor 14, the central anchoring portion 33 is fitted through the two openings in the guide tube 12 and the opening in the cable nipple 34, as can be seen fran Figures 1, 2 and 7.

The other end of the guide tube 12, which is thus at the right in Figure 1, is fixedly connected to a locking member 11. The locking member 11 is of an annular configuration thus providing an internal bore therethrough. The tension cable 28 which extends fran the other left-hand end of the guide tube 12 through the guide tube 12 passes through the bore in the locking mr 11 outwardly to the safety belt webbing which is to be tightened, for example to the belt lock, with 6 the possible interposition of a device for preventing a return rriotion, as is to be found in EP 0 398 010 A2.

The locking levers 7 are supported on the locking m=ber 11 pivotably about axes of rotation as indicated at 17, thus defining first and second sides or portions m each lever 7. Each lever 7 bas on the one lever side or portion which is disposed between the locking ffeTber 11 and the spring plate 9 a support location 2 3 at which the lever bears against or is engaged with the locking ne 11, and also a second support location 22 where the lever bears against the spring plate 9. The two support locations 22 and 23 extend at least substantially perpendicularly to the axis A of the compression coil spring 13 or to the direction of the drive force produced by the compression coil spring 13. The locking member 11 and the spring plate 9 have corresponding support locations so that there is a positive locking connection between the support locations on the respective locking lever 7 and the support locations on the locking wr 11 and the spring plate 9. The support locations 22 and 23 are arranged displaced relative to each other, with respect to the axis A of the compression coil spring 13, with the support location 23 on the locking manber 11 being closer to the axis A than the support location 22 on the spring plate 9. The axis of rotation 17 of the respective locking lever 7 is disposed between the support locations 22 and 23, with respect to the spacing relative to the axis A. The axis of rotation 17 of the respective locking lever lies on the circular outer periphery of the locking we 11, in other words, the axes of rotation 17 of the locking levers 7 are arranged on a circle around the axis Aof the compression coil spring. As already described above the spring plate 9 is supported stationarily against the carrier 3 which is suitably connected to the vehicle structure or chassis. The contact pressure forces which act at the support locations 22 and 23 between the one locking lever am and the locking nE 11 and the 7 spring plate 9 are provided by the drive force in the drive direction indicated by the arrow B in Figures 1 and 2 produced by the prestressed compression coLl spring 13. For that purpose the locking mnber 11 is connected by way of the guide tube 12 to the other end of the spring by means of the spring anchor 14, as already described above. That arrangement provides a respective torque which acts on the locking lever 7 about its axis of rotation 17.

Between the support locations 22 and 23 the locking lever 7, at an engagement portion 19 thereof which is disposed between the locking mnber 11 and the spring plate 9, has an inclined surface or edge 20 which corresponds in regard to its configuration to an inclined surface 21 on the spring plate 9, the surface 21 being disposed outside the support location 22 with respect to the axis A. As will be described in greater detail hereinafter, the two inclined surfaces 20 and 21 on the respective locking lever 7 and on the spring plate 9 act in a way such as to release the assembly frcm the illustrated locking position, after increased or excessive braking or acceleration of the motor vehicle.

To provide for simplified assembly it is possible to use an assembly ring 8 which holds in position the three locking levers7 which are arranged at equal angular spacings about the axis A. For that purpose the assembly ring can firstly be fitted into an assembly recess 10 on the respective levers and after final assembly of the other cnents, in particular a sensor mass body 4 which will be described hereinafter, moved into the position shown in Figures 1 and 2.

The lever arms at the other side of each of the double-sided locking levers 7 a supported on the above-mentioned sensor mass formed by a sensor mass body 4. For that purpose the sensor mass body 4 has abutments 25 and 26 which, as shown in Figure 6, are arranged at 8 corresponding angular spacings on the sensor mass body 4 at positions corresponding to the angular positions of the three locking levers 7 about the c-xis A. As can be seen more particularly from Figures 2 and 4, the end portions 27 of the lever arms are of a T-shape configuration with lateral, transversely extending end portions 35 and 36 at each side of the respective lever. In that way, formed on the lever arm at both sides thereof at the end of the lever are abutment surfaces which bear against the respective co-operating abutments 25 and 26 on the sensor mass body 4, as can be seen from Figure 6. That configuration provides for halving of the contact pressure force with which each locking lever 7 bears against the sensor mass body 4, at the two abutments 26 and 27 for each lever. The contact pressure force of the respective locking lever 7 against the sensor mass body 4 is produced by the prestressed compression coil spring 13 which, as already described above, acts by way of the locking mwdmr 11 on the other lever arm at the other side of the locking lever 7 in the region of engagement of the locking lever 7, that is to say, at the support location 23. The drive force produced by the compression coil spring 13 in the direction indicated by the arrow B produces the above- mentioned turning mament or torque tending to pivot the respective locking lever 7 about the axis of rotation 17, that ncment or torque resulting in the respective half of the contact pressure force applied by the lever arm end 27 against the respective abutments 25 and 26.

Referring to Figures 1 to 3. in the embodiment illustrated 25 herein, the sensor mass body 4 is mounted movably in the axial direction on a roller 5 to provide a low-friction bearing configuration. The sensor mass body 4 is biased in a direction in opposite relationship to the direction of the drive force of the ression coil spring 13 by a sensor spring 6 which is also in the form of a compression coil spring. In the prestressed condition of the 9 ccrnpression coil spring 13 the sensor mass body 4 bears against the two transversely extending end portions 35, 36 at the respective end 27 of the lever arm of the locking lever 7, as can be seen from Figure 2. The two transversely extending end portions 35 and 36 therefore form an abutment for defining the limit position in the prestressed condition which is also the rest condition of the belt tightener. The transversely extending end portions 35 and 36 which, as described above, also bear by way of corresponding abutment surfaces against the abutments 25 and 26 thus perform a dual function in the illustrated embodiment. It will be appreciated however that it is also possible for the abutment for defining the limit position of the sensor mass body 4 to be defined in a different fashion, for example by bearing against an end face of a sensor mass cover which is indicated by reference 1 in Figure 1 and which is connected to the protective tube 2 and which is suitably adapted to the shape of the sensor mass body 4, as is shown by Figures 1 to 6. However, the form of abutment which is defined by the transversely extending end portions 35 and 36 is preferred. That provides for exact dmTensioning of the release distance F fram the rest position of the sensor mass body 4 into a position in which the T-shaped lever arm ends 27 move into openings or recesses 24 on the sensor mass body 4, for release of the engagement of the respective locking lever 7 into the locking nr 11.

As can be seen frcxn Figure 1 the sensor spring 6 is arranged on a sensor carrier 18 which is supported on the carrier 3 or which is integral therewith.

In addition, in the embodiment illustrated roller bearing means are provided m the carrier 3, in the form of bearing arms 37 to 40. Figure 1 is a side view of the roller bearing means at one side while Figures 3 and 4 show views in section through the roller bearing assembly. The roller 5 is guided in the roller bearing arms 37, 38 and 39, 40 and is rollingly mounted therein. The sensor mass body 4 is also mounted m the roller 5 in such a way as to roll along thereon. That configuration provides for low-friction mounting of the sensor mass body 4 relative to the carrieu: 3 which is fixed to the vehicle structure. At the underside the sensor mass body 4 can be suitably adapted to the configuration of the roller 5, as shown in Figure 3. For that purpose bevelled guide rail portions 41 and 42 for example can be formed on the underside of the sensor mass body 4. The roller 5 is provided with correspondingly shaped bevelled rolling surfaces at each of its two ends. In conjunction with additional guide elements 45 and 46 which are shown in section in Figure 5 and which are provided on the sensor mass body 4 and correspondingly shaped guide portions 47 and 48 which are formed at the underside of the cover 1, that arrangement provides that the sensor mass body 4 is precisely axially guided. It is also possible however for the roller 5 to be provided at its ends with suitable flange portions which are in engagement with suitably shaped recesses at the underside of the sensor mass body 4, to provide for the desired axial guidance effect.

If an increased acceleration or deceleration effect above a specific level acts on the vehicle, for exwple as a result of an accident situation, the resulting force acts directly on the sensor mass body 4 mounted on the carrier 3 and thereby on the vehicle structure so that the sensor mass body 4 is moved in opposition to the force of the sensor spring 6 at least by the release distance indicated at F in Figures 1 and 2. In that situation, the edges, which are at the left in Figures 1 and 2, of the transversely extending end portions 35 and 36 of the ends 27 of the locking levers 7 are moved beyond the right-hand edges of the abutments 25 and 26 and are pivoted into the openings or recesses 24 in the sensor mass body 4 by virtue of the torque imparted by the compression coil spring 13. That pivotal movement occurs about the axes of rotation 17 which are defined m the locking nr 11 so that the inclined surface 20 on each locking 11 lever 7 comes into the region of the inclined surface 21 on the spring plate 9. The locking member 11 then still bears in the outer edge regions of the support locations 23 against the locking levers 7 and the drive force acting on the locking Mr 11 in the direction of the arrow B causes the locking levers 7 which bear with their inclined surfaces 20 at the inclined surfaces 21 against the spring plate 9 to be moved radially outwardly relative to the axis A. For release of the locking assembly, two movemnts take place, namely the pivotal movement of the locking levers 7 about their axes of rotation 17 and the radial movement of the locking levers 7 outwardly, by virtue of the co-operation of the inclined surfaces 20 and 21 on the locking levers 7 and on the spring plate 9. The required force is produced by the compression coil spring 13 in the drive direction as indicated by the arrow B in Figures 1 and 2. The beginning of the movement which acts on the safety belt to tighten same by way of the tension cable 28 is used for releasing the engagement of the locking levers 7 from the locking mr 11. The required pivotal angle which the lever arm ends 27 must perform to release the locking engagement can be relatively small because the definitive release movement of the locking levers 7 is produced by the co-operation of the inclined surfaces 20 and 21.

In the movement of the sensor mass body 4 the roller 5 rolls against both the underside of the sensor mass body 4 and also the lower mounting arms 38 and 40. If the acceleration or deceleration force acting on the belt tightener is below a predetermined threshold, the sensor mass body 4 can perform axial movements which are shorter than the release distance F. In that situation, due to the force of the sensor spring 6, the sensor mass body 4 is moved back again into its starting position in which it bears against the tranversely extending end portions 35 and 36 of the locking levers 7, more specifically by way of its abutments 25 and 26. That movement of the sensor mass body 4 does not affect the locking condition illustrated.

12 The drive movement of the released compression coi 1 spring 13 is transmitted to the tension cable 28 which is passed out of the belt tightener through a bowden cable casing 43. The casing 43 is fixed to the carrier 3 by a suitable fixing clip 44 as shown in Figures 1 and 6. A securing fork 49 serves to de-activate or secure the release arrangement of the belt tightener during assembly thereof. After assembly the fork 49 is removed so that the belt tightener is then activated or in a condition of readiness.

It will be seen fran the foregoing therefore that the response characteristic in relation to acceleration or deceleration above a given level is substantially independent of the ccopression coil spring 13 forming the force storage means for producing the drive force to act on the belt webbing to tighten sane. Furthermore, while retaining the advantage that the vehicle-sensitive sensor system acts directly on the locking configuration, the above-described configuration according to the invention give the advantage that the campression coil spring can be independent of the inertia-sensitive mass formed by the sensor mass body 4, which is required for operation of the sensor system. It is possible for example to use relatively light springs to produce the tension force required for producing the drive effect in the belt tightening phase. By virtue of the fact however that the locking levers which form the locking configuration remain directly coupled to the vehicle-sensitive sensor mass, that is to say the sensor mass body 4, by way of the abutments 25 and 26 thereon, that arrangemeent affords direct co-operation between the locking configuration and the sensor system without the need for that purpose of intermediate members such as additional levers or like transmission ccmponents. The belt tightener described above can also provide for adaptation to the respective release characteristics of the various types of vehicles to which the belt tightener is to be fitted.

13 It will be appreciated that the above-described embodIment of the belt tightener according to the invention has been set forth solely by way of ex"le and illustration of the invention and that various modifications and alterations may be made therein without thereby departing from the spirit and scope of the invention as defmed by the appended claim.

Claims

14 CLAIMS:

1. A belt tightener for a vehicle safety belt ccmprising: a compression coil spring as a force storage means for producing a drive force to act on the safety belt to tighten same; a locking weans for holding the ccopression coil spring in a prestressed condition, including a locking member movable upon release of the compression coil spring by said drive force, and a plurality of double-sided locking levers arranged around the axis of the compression coil spring and having axes of rotation arranged on a circle around the axis of the compression coil spring on said locking member, the locking levers engaging said locking member at their one lever side; a sensor mass body mounted mvably relative to the vehicle structure by an increased acceleration or deceleration acting on the sensor mass body in the axial direction of the compression coil spring; and abutment means on the sensor mass body, the locking levers bearing with their other lever side against the abutment means in the rest condition, the arrangement being such that to release the drive force of the prestressed compression coil spring the abutment weans and the locking levers are movable relative to each other and the locking levers are pivotable about their axes of rotation on the locking member.

2. A belt tightener according to claim 1 wherein the sensor mass body is movable towards the axes of rotation of the locking levers.

3. A belt tightener according to claim 1 or claim 2 wherein the sensor mass body has openings into which the locking lever portions which bear against the abutment means are moved for release of the locking member when the sensor mass body has moved a certain release distance.

4. A belt tightener according to claim 3 wherein said lever portions are moved into the openings in the sensor mass body by the drive force of the compression coil spring.

5. A belt tightener according to any one of the preceding claims wherein the drive force of the ccopression coil spring only acts on the locking levers in the drive force direction at the sides of the locking levers which are remote from the abutment means.

6. A belt tightener according to any one of the preceding claims wherein the sensor mass body is movable against the force of a sensor spring which in use is supported at the vehicle structure.

7. A belt tightener according to any one of the preceding claim wherein the compression coil spring is supported at one end thereof at the vehicle structure.

8. A belt tightener according to claim 6 wherein the force applied to the sensor mass body by the sensor spring is in opposite relationship to the direction of the drive force of the ression coil spring.

9. A belt tightener according to any one of the preceding claim wherein each locking lever bears against first and second abutment portions of the respectively associated abutment weans so that the contact pressure of the locking lever against said abutment weans is halved.

10. A belt tightener according to claim 9 wherein the end portion of the locking lever which bears against the first and second abutment portions is substantially T-shaped.

11. A belt tightener according to any one of the preceding claims wherein the release distance by which the sensor mass body is movable for release of the locking nember is determined by the axial extents of the abutment means and the contact surfaces co-operable therewith on the locking levers.

16

12. A belt tightener according to any one of the preceding claims wherein the sensor mass body is mounted movably by way of a rolling bearing means.

13. A belt tightener according to any one of the preceding claims including a tension cable for applying the belt tightening force, connected to an end portion of the compression coil spring, and an additional connecting means connecting said end portion of the compression coil spring to the locking mewber.

14. A belt tightener according to claim 13 wherein said additional connecting means is in the form of a guide tube disposed in the interior of the compression coil spring and wherein the tension cable is guided by the guide tube and a bore in the locking member in a direction towards the belt to be tightened.

IS. A belt tightener according to any one of the preceding claims including a carrier supporting the compression coil spring and a sensor spring acting on the sensor mass body on the vehicle structure.

16. A belt tightener according to claim 15 wherein the sensor spring is arranged substantially on the axis of the compression coil spring.

17. A belt tightener according to claim 15 when appendant to claim 12 wherein the roller bearing means for the sensor mass body is provided m said carrier.

18. A belt tightener according to claim 12 or any claim appendant thereto wherein the rolling bearing weans further serves to guide the sensor mass body in the axial direction of the compression coil spring.

D

19. A belt tightener according to claim 15 when appendant to claim -12 wherein the roller bearing means mrprises at least one roller rolling on said carrier.

20. A belt tightener for a vehicle safety belt substantially as hereinbefore described with reference to the accompanying drawings.

21. A safety belt assembly for a motor vehicle, including a belt tightener according to any one of the preceding claim.