MODULAR SYSTEM FOR A BELT TIGHTENER COMPRISING A SPUR GEAR MECHANISM, AND BELT TIGHTENER

Abstract

A modular system (11) for a belt tensioner (10) comprising a spur gearing (18) comprises plural step wheel pairings of a first step wheel (28) and a second step wheel (30), wherein for each of the step wheel pairings the number of teeth of the first step wheel (28) and the number of teeth of the second step wheel (30) are different from those of the other step wheel pairings, but the distance between a shaft (44) of the first step wheel (28) and the shaft (44) of the second step wheel is equal for each of the step wheel pairings. In addition, the modular system (11) comprises identically designed housings (20) into each of which a spur gearing (18) with one of the step wheel pairings can be introduced.

Claims

1-10. (canceled)

11. A modular system for a belt tensioner (10) comprising a spur gearing (18), wherein the spur gearing (18) includes at least one motor gearwheel (26) and at least a first step wheel (28) and a second step wheel (30), the motor gearwheel (26) forming a first gear stage (34) with the first step wheel (28) and the first step wheel (28) forming a second gear stage (36) with the second step wheel (30), wherein the modular system (11) includes plural step wheel pairings of the first step wheel (28) and the second step wheel (30), wherein the modular system (11) includes identically designed housings (20) into each of which a spur gearing (18) with one of the step wheel pairings can be introduced, wherein each first step wheel (28) and each second step wheel (30) has an opening (42) axially passing through the respective step wheel (28, 30) for holding a shaft (44), a bearing point of the housing (20) being associated with each shaft (44), and wherein, for each of the step wheel pairings, the number of teeth of the first step wheel (28) and the number of teeth of the second step wheel (30) are different from those of the other step wheel pairings, but the distance between the shaft (44) of the first step wheel (28) and the shaft (44) of the second step wheel (30) is equal for each of the step wheel pairings.

12. The modular system according to claim 11, wherein the sum of the numbers of teeth of the first step wheel (28) and the second step wheel (30) in the second gear stage (36) is equal for each of the step wheel pairings.

13. The modular system according to claim 11, wherein each gearwheel (26, 28, 30, 32) inserted in the belt tensioner (10) has an opening (42) axially passing through the respective gearwheel (26, 28, 30, 32) for holding a shaft (44) and a bearing point of the housing (20) is associated with each shaft (44), and wherein each distance between two of the shafts (44) at a time is equal for each of the step wheel pairings.

14. The modular system according to claim 11, wherein the first gear stage (34) is arranged to be closer to a lower side (22) of the housing (20) than the second gear stage (36).

15. The modular system according to claim 11, wherein the size of the identically designed housings (20) is adapted to hold the step wheel pairing with the highest space requirement.

16. The modular system according to claim 11, wherein at least two meshing gearwheels (26, 28, 30, 32) of the spur gearing (18) have a helical gear, specifically the first step wheel (28) and the second step wheel (30).

17. The modular system according to claim 11, wherein each of the step wheel pairings includes a visual identifier (50).

18. The modular system according to claim 11, wherein the modular system (11) comprises plural electric motors (40) which can be operated at different voltages, and/or an electric motor (40) which can be operated at least at two different voltages, the electric motor (40) in the belt tensioner being connected to the motor gearwheel (26) for driving the motor gearwheel (26).

19. The modular system according to claim 11, wherein the step wheels (28, 30) of the step wheel pairings are manufactured using an injection molding process and/or using a sintering process.

20. A belt tensioner which is manufactured by a modular system (11) according to claim 11.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Further benefits and characteristics of the invention will result from the following description of exemplary embodiments which should not be understood in a limiting sense, and from the drawings, wherein:

[0074] FIG. 1 shows a top view onto selected parts of a first embodiment of a belt tensioner according to the invention that was manufactured using a modular system according to the invention,

[0075] FIG. 2 shows a top view onto a step wheel gearing of the belt tensioner of FIG. 1,

[0076] FIG. 3 shows a perspective view of parts of the step wheel gearing of FIG. 2,

[0077] FIG. 4 shows a top view onto a step wheel gearing of a second embodiment of the belt tensioner according to the invention, and

[0078] FIG. 5 shows a top view onto a step wheel gearing of a third embodiment of the belt tensioner according to the invention.

DESCRIPTION

[0079] FIG. 1 illustrates a first embodiment of a belt tensioner 10 according to the invention that can be used in a seatbelt system, such as in a seatbelt system for vehicle occupants.

[0080] The belt tensioner 10 is manufactured by a modular system 11 (see FIG. 2).

[0081] The belt tensioner 10 is connected to a frame 12 of a belt retractor 14 in which a belt reel 16 is rotatably supported to wind up, for example, webbing (not shown) and to eliminate a belt slack, when the belt retractor 14 is triggered.

[0082] The belt tensioner 10 has a spur gearing 18 which is held in a housing 20. The housing 20 comprises a lower side 22 of the housing 20 and a housing cover 24.

[0083] FIG. 2 illustrates a top view onto the spur gearing 18 which is used in the belt tensioner 10 of FIG. 1.

[0084] The spur gearing 18 is held in its mounting position in the housing 20 of the belt tensioner 10 (see FIG. 1), the modular system 11 comprising identically designed housings 20 into each of which a spur gearing 18 can be introduced.

[0085] It can be seen from FIG. 2 that the spur gearing 18 includes a motor gearwheel 26, also referred to as motor pinion, a first step wheel 28, a second step wheel 30 and a third step wheel 32.

[0086] The motor gearwheel 26 and the first step wheel 28 form a first gear stage 34, the first step wheel 28 and the second step wheel 30 form a second gear stage 36, and the second step wheel 30 and the third step wheel 32 form a third gear stage 38.

[0087] It is understood that the modular system 11 can also provide exclusively a first gear stage 34 and a second gear stage 36 or more than three gear stages.

[0088] In the shown embodiment, the motor gearwheel 26, the first step wheel 28, the second step wheel 30 and the third step wheel 32 are made by an injection molding process and are made of synthetic material.

[0089] Basically, the motor gearwheel 26, the first step wheel 28, the second step wheel 30 and/or the third step wheel 32 can also be made of a metal or a metal alloy and can be manufactured using a sintering process, for example.

[0090] The motor gearwheel 26 is driven by means of an electric motor 40 (indicated only schematically), wherein the motor gearwheel 26 can be driven either clockwise or anti-clockwise. In other words, the shown belt tensioner 10 is a reversible belt tensioner.

[0091] The modular system 11 has plural electric motors 40 which can be operated at different voltages.

[0092] The electric motor 40 of the first embodiment of the belt tensioner 10 is an electric motor that is designed for an operating voltage of 12 V. The operating voltage is provided, for example, via an onboard power supply of a vehicle (not shown) in which the belt tensioner 10 is installed.

[0093] All gearwheels involved in the spur gearing 18, i.e., the motor gearwheel 26, the first step wheel 28, the second step wheel 30 and the third step wheel 32, include an opening 42 axially passing through the respective gearwheel.

[0094] A shaft 44 associated with the corresponding gearwheel is arranged in each of said openings 42.

[0095] The distance between the shafts 44, also referred to as center distance, in FIG. 2 is referred to as a1, a2 and/or a3, wherein the center distance a1 indicates the distance between the shafts 44 of the motor gearwheel 26 and the first step wheel 28, the center distance a2 indicates the distance between the shafts 44 of the first step wheel 28 and the second step wheel 30, and the center distance a3 indicates the distance between the shafts 44 of the second step wheel 30 and the third step wheel 32.

[0096] In addition, in FIG. 2 a center distance a4 is plotted which denotes the distance between the shaft 44 of the third step wheel 32 and a retractor shaft 46 of the belt retractor 14.

[0097] The first step wheel 28 and the second step wheel 30 form a step wheel pairing of the modular system 11 according to the invention, the modular system 11 comprising plural step wheel pairings.

[0098] For each of the step wheel pairings, the number of teeth of the first step wheel 28 and the number of teeth of the second step wheel 30 are different from those of the other step wheel pairings, while the center distance a2 is equal for each of the step wheel pairings.

[0099] In the shown embodiment, moreover the sum of the numbers of teeth of the first step wheel 28 and the second step wheel 30 in the second gear stage 36 is equal for each of the step wheel pairings.

[0100] Basically, the number of teeth between different step wheel pairings can also be different from each other, as long as the resulting center distance can further be designed to be constant. For example, this is also possible by the selection of a helix angle, the standard module or the profile modification factor.

[0101] The total transmission ratio of the step wheel gearing 18 results as a product of the intermediate gear transmissions of all gear stages as well as the gear stage between the last step wheel and the belt retractor 14, i.e., between the third step wheel 32 and the belt retractor 14 in the shown embodiment.

[0102] For example, the spur gearing has a total transmission ratio of 32.

[0103] The modular system 11 according to the invention enables the total transmission ratio of the spur gearing 18 to be adapted and defined exclusively by a change of the step wheel pairing used, i.e., in the shown embodiment by the selection of the numbers of teeth of the first step wheel 28 and the second step wheel 30 in the second gear stage 36.

[0104] Thus, the center distances a1 to a4 can remain unchanged for each selected step wheel pairing so that no further components of the belt tensioner 10 have to be adapted when the total transmission ratio of the spur gearing 18 is to be adapted.

[0105] FIG. 3 illustrates a perspective view of selected parts of the spur gearing 18 of FIG. 1.

[0106] In this representation, the shafts 44 which axially pass through the first step wheel 28 and the second step wheel 30 can be recognized even more clearly than in FIG. 2. In addition, it is evident that the shafts 44 each merge into a collar-type projection 38 at a lower axial end, the projections being assigned to bearing points (not shown in detail) of the lower side 22 of the housing 20 (see FIG. 1).

[0107] It can moreover be seen from FIG. 3 that the motor gearwheel 26, the first step wheel 28 and the third step wheel 30 have a helical gear.

[0108] The helical gear allows improved quiet running and a desired load distribution at the bearing points of the respective gearwheels by the selection of the overlap ratio and/or the helix angle of the helical gear.

[0109] Also, one can see that the first gear stage 34 is arranged to be closer to the lower side 22 of the housing 20 (see FIG. 1) than the second gear stage 36.

[0110] FIG. 4 represents a top view onto the step wheel gearing 18 of a second embodiment of the belt tensioner 10 which was manufactured by means of the modular system 11 according to the invention.

[0111] The second embodiment substantially corresponds to the first embodiment so that hereinafter only differences shall be discussed. Like reference signs characterize like component parts, and reference is made to the foregoing explanations.

[0112] In the second embodiment, the first step wheel 28 in the second gear stage 36 has a lower number of teeth and the second step wheel 30 in the second gear stage 36 has a larger number of teeth than in the first embodiment. In other words, in the manufacture of the belt tensioner 10, a different step wheel pairing was selected than for the first embodiment.

[0113] The further components of the step wheel gearing 18 are unchanged, however, in particular the transmission ratios in the first gear stage 34, in the third gear stage 38 and between the third step wheel 32 and the belt retractor 14 are equal.

[0114] Thus, the belt tensioner 10 of the second embodiment has a higher total transmission ratio than in the first embodiment, for example a total transmission ratio of 46.

[0115] The center distances between the gearwheels involved are equal to the first embodiment of the belt tensioner 10 so that no adaptations have to be made to the housing 20.

[0116] The second step wheel 30 in the second embodiment additionally includes an optical identifier 50 to avoid confusions with other second step wheels 30 of the modular system 11. In the shown embodiment, the optical identifier 50 is a barcode.

[0117] Basically, also a different clear identification mark, such as a part number, a part designation, a surface contouring, a QR code and/or a color marker, can be used as an optical identifier 50, however.

[0118] Due to the higher transmission ratio, the belt tensioner is suited, when the electric motor 40 operated at 12 V is used, to be inserted in a seatbelt system which is intended to allow repositioning of the vehicle occupant.

[0119] It is also possible to select an electric motor 40 of the modular system 11 which can additionally be operated at 48 V, for example by the electric motor 40 being temporarily overloaded. In this event, the webbing can be fully tensioned due to the higher transmission ratio of the belt tensioner 10 so that the use of additional pyrotechnic compositions can be dispensed with.

[0120] FIG. 5 represents a top view onto the step wheel gearing 18 of a third embodiment of the belt tensioner 10 that was manufactured using the modular system 11 according to the invention.

[0121] The third embodiment substantially corresponds to the first and second embodiments so that hereinafter only differences shall be discussed. Like reference numerals characterize like component parts, and the foregoing explanations are referred to.

[0122] In the third embodiment, the first step wheel 28 in the second gear stage 36 has a higher number of teeth, and the second step wheel 30 in the second gear stage 36 has a lower number of teeth than in the first embodiment. In other words, when manufacturing the belt tensioner 10, yet another step wheel pairing was selected than for the first and second embodiments.

[0123] The further components of the step wheel gearing 18, apart from the electric motor 40, are unchanged, however, in particular the transmission ratios in the first gear stage 34, in the third gear stage 38 and between the third step wheel 32 and the belt retractor 14 are equal.

[0124] Consequently, the belt tensioner 10 of the third embodiment has a lower total transmission ratio than in the first embodiment, for example a total transmission ratio of 24.

[0125] The center distances between the gearwheels involved are equal to the first and second embodiments of the belt tensioner 10 so that no adaptations have to be made to the housing 20.

[0126] Due to the lower transmission ratio, the belt tensioner 10 of the third embodiment is suited to make use of an electric motor 40 that is designed for operation at a voltage of 48 V, i.e., can generate a higher torque than an electric motor that is designed for operation at 12 V. The lower total transmission ratio allows the belt tensioner 10 to be further used for applications in which only low forces have to be generated, for example the reduction of the belt slack, whereas even for use scenarios in which high forces have to be generated, such a full tensioning, the same belt tensioner 10 can be used. In other words, the belt tensioner 10 of the third embodiment can make the use of pyrotechnic compositions superfluous.

[0127] The modular system 11 according to the invention allows to manufacture different belt tensioners 10 which are suitable for different desired use scenarios with low effort.

[0128] In particular, only those first step wheels 28 and second step wheels 30 which include the currently required number of teeth have to be manufactured in the ongoing production process, while the further components of the belt tensioner 10 can remain unchanged. Thus, a flexible and customized production of the belt tensioners 10 can be realized.