Module system for a belt tensioner with a springle gearing device and belt tensioner

Abstract

The invention relates to a modular system (11) with a spur gear (18) for a belt tensioner (10), comprising a plurality of stepped gear pairs consisting of a first stepped gear (28) and a second stepped gear (30), the number of teeth of the first stepped gear (28) and the number of teeth of the second stepped gear (30) being different from the number of teeth of the other stepped gear pairs for each stepped gear pair, however, the distance between the shaft (44) of the first stepped gear (28) and the shaft (44) of the second stepped gear is the same for each of the stepped gear pairs. The module system (11) further comprises housings (20) of the same design, in each of which a spur gear (18) with one of the stepped gear pairs can be inserted.

Description

Technical Field

[0001] The invention relates to a module system with a spur gear transmission for a belt tensioner, in particular for a belt tensioner of a seat belt system, and to a belt tensioner produced from such a module system. Background Art

[0002] Belt tensioners are used to reduce certain influences that negatively affect the restrained vehicle occupants in a restrained situation before they move forward and, if necessary, begin to use force limiting devices. These influences include, for example, the so-called film effect and belt slack. The film effect refers to the loose winding of the belt webbing on the belt reel. In the case of belt slack, the belt webbing only rests loosely on the vehicle occupant. The belt tensioner reduces belt slack and the film effect in a very short time by, for example, winding the belt webbing onto the belt reel of the belt retractor and thereby tightening the belt webbing. The vehicle occupants can thus participate in the deceleration of the vehicle at an early stage. In addition, the conditions for the subsequent use of force limiting devices are also improved.

[0003] Belt tensioners are already known in which, in the event of a triggering, a pyrotechnic component is ignited which drives the retractor. Such belt tensioners can only be triggered once and are designed for fully tensioned load situations, that is, for situations in which a vehicle occupant should be secured as quickly as possible and with great force.

[0004] Also known are belt tensioners that are driven by means of an electric motor, in particular so-called reversible belt tensioners. In this context, "reversible" means that the belt reel can be driven in both directions, so that on the one hand the belt webbing can be tensioned and on the other hand the tensioning can also be reversed. For tensioning, the electric motor must provide a high torque at a high rotational speed in order to be able to tension the belt with sufficient force and speed. The advantage of using an electric motor as a drive device in a belt tensioner is in particular the possibility of operating the belt tensioner multiple times.

[0005] However, such belt tensioners driven by means of electric motors are usually optimized and designed for the fully tensioned load case.

[0006] For example, the electric motor is driven by the 12 V on-board power supply of a vehicle using a belt tensioner, the maximum supply current of which is in the range of 20 to 40 A. The transmission ratio of the transmission of such a belt tensioner is usually in a narrow range of 30 to 35. Under these framework conditions, a tensioning force in the range of about 100 to 300 Newtons can be achieved in a time of about 100 to 150 milliseconds, which acts on the shoulders of the vehicle occupants.

[0007] However, such belt tensioners designed for full tensioning cannot be used without problems for different alternative or additional application scenarios or adapted for them in a simple manner. However, this is undesirable in order to be able to implement other functions of the seat belt system, such as warning functions or repositioning of the vehicle occupant by means of the belt webbing. However, these different applications usually require different transmission ratios, which must be complex to create and implement via their own transmission and housing development. Summary of the invention

[0008] The object of the present invention is to provide a possibility for producing a belt tensioner which can be adapted to different application scenarios in a resource-saving and simple manner.

[0009] The object is achieved by a modular system for a belt tensioner with a spur gear transmission, wherein the spur gear transmission comprises at least one motor gear and at least one first and second step gear, wherein the motor gear and the first step gear form a first transmission stage and the first step gear and the second step gear form a second transmission stage. The modular system comprises a plurality of stepped gear pairs consisting of a first and a second step gear. The modular system further comprises identically designed housings, into which a spur gear transmission with one of the stepped gear pairs can be installed. Each first and second step gear has an opening for accommodating a shaft, through which the respective stepped gear is axially passed, wherein each shaft is associated with a bearing point of the housing. For each of the stepped gear pairs, the number of teeth of the first step gear and the number of teeth of the second step gear differ from the number of teeth of the other stepped gear pairs, but the distance between the axis of the first step gear and the axis of the second step gear is the same for each of the stepped gear pairs.

[0010] The basic idea of ​​the invention is that the belt tensioner is produced in a modular system, the housing of the respective belt tensioner being always identical.

[0011] In other words, the modular system according to the invention enables a high degree of standardization by using as many identical components as possible, i.e. identical components of the modular system. In this way, the complexity in the production of belt tensioners manufactured with the aid of the modular system is reduced, while at the same time the flexibility in the manufacturing process can be increased. In this way, customer wishes can be responded to in a demanding manner. In addition, the warehousing of components and different types of belt tensioners can be simplified, thereby reducing the overall production costs of the belt tensioners.

[0012] In known belt tensioners, if different transmission ratios are to be realized, a large number of belt tensioner components must be adapted to realize additional or alternative applications. In particular, all participating gear wheels, their bearing locations, the shape of the housing and any covers, and the type and positioning of the motor or electric motor must be adapted.

[0013] In the modular system according to the invention, however, only the first step gear and the second step gear need to be adapted, and only the toothing of the respective step gear used in the second transmission stage needs to be adapted.

[0014] In other words, according to the invention, the overall transmission ratio of the transmission of the belt tensioner can be adapted via the transmission ratio of the second transmission stage, while the other intermediate transmission ratios in all other transmission stages remain unchanged.

[0015] According to the invention, the distance between the shaft associated with the first stepped gear of the respective stepped gear pair and the shaft associated with the second stepped gear of the respective stepped gear pair is the same for each stepped gear pair and is therefore also referred to as a “constant wheelbase”.

[0016] In other words, according to the invention a constant wheelbase is ensured, regardless of the respectively selected stepped gear pair, in order to standardize the design of the surrounding components of the belt tensioner.

[0017] The “constant wheelbase” can be defined by the following formula (1):

[0018]

[0019] Where a represents the wheelbase of the second transmission stage, z1 represents the number of teeth of the first step gear, z2 represents the number of teeth of the second step gear, and m n represents the normal modulus, β represents the helix angle and x1 to x n Indicates other tooth parameters, such as tooth profile modification coefficient.

[0020] In other words, according to the invention, it is provided in particular that the wheelbase is constant for each stepped gear pair of the module system in that the above formula (1) is satisfied for each stepped gear pair of the module system.

[0021] Accordingly, while all other parameters in formula (1), such as normal module, helix angle and tooth profile modification coefficient, remain constant between different step gear pairs, only the sum of the number of teeth of the first step gear and the second step gear must remain constant in each step gear pair.

[0022] If, however, at least one other parameter changes for one of the stepped gear pairs of the modular system, the sum of the number of teeth of the first and second stepped gear of the stepped gear pair must be adapted in such a way that it is also ensured that the wheelbase a according to formula (1) remains constant.

[0023] It goes without saying that the wheelbase actually achievable in a belt tensioner obtained with the modular system according to the invention can deviate from the theoretical value determined according to formula (1) due to unavoidable necessary adaptations, such as the backlash to be taken into account.

[0024] In a variant, the sum of the number of teeth of the first and second step gears in the second transmission stage is the same for each step gear pair. In such a modular system, the complexity of the step gear pairs to be provided is reduced, but the belt retractor that can be manufactured using the modular system can only be adapted in such a way that no other parameters are adapted according to equation (1).

[0025] The shafts that match the respective stepped gears are also part of the modular system.

[0026] In order to securely fix the shafts, they can be injection-molded around with plastic at the respectively associated bearing points of the housing, ie, the shafts can be fixed by means of an injection-molded connection.

[0027] Particularly preferably, each gear used in the belt tensioner has an opening for receiving a shaft axially through the respective gear and each shaft is associated with a bearing point of the housing, wherein each distance between each two shafts is the same for each stepped gear pair.

[0028] In other words, all wheelbases in the belt tensioner are independent of the respective stepped gear pair. In this way, the number of necessary adaptations in the belt tensioner for different stepped gear pairs of the modular system is reduced to a minimum, and particularly preferably no further adaptation of the components of the modular system is required apart from the correspondingly selected stepped gear pairs.

[0029] Furthermore, here and in the following, the expression "each gear used in the belt tensioner" refers to the motor gear (also called motor pinion) and possibly other gears, such as other stepped gears.

[0030] Furthermore, for each of the stepped gear pairs, the axis distance between the take-up shaft of the belt retractor of the belt tensioner and the axis of the gear used in the belt tensioner may also be the same.

[0031] In order to further simplify the assembly of the belt tensioner, in the installed position the first transmission stage can be arranged closer to the underside of the housing than the second transmission stage.

[0032] In other words, in this variant, first the motor with the motor pinion, then the first step gear and possibly further step gears except the second step gear and then the second step gear can be installed during production of the belt tensioner, ie installed in the underside of the housing.

[0033] The size of the housing of identical configuration is particularly adapted to accommodate the stepped gear pair with the highest structural space requirement. In other words, the stepped gear pair with the stepped gear of the maximum size can also be installed in the housing in order to reach the desired transmission ratio without any other adaptation.

[0034] The housing is designed in particular as a multi-part housing which comprises a housing cover which is provided for closing the housing after the spur gear has been installed.

[0035] The housing cover can also provide bearing points which match the gears involved in the transmission of the belt tensioner or shafts passing through the gears and ensure secure fixing and orientation.

[0036] In another variant, at least two meshing gears of the spur gear mechanism, in particular the first stepped gear and the second stepped gear, have helical toothing.

[0037] The use of gears with helical teeth improves the running smoothness of spur gears and increases their service life.

[0038] Preferably, both the motor gear and the stepped gear of the stepped gear transmission have helical gearing. In other words, the gear with helical gearing can be used in a plurality of transmission stages, in particular in all transmission stages.

[0039] In this case, the helix angle of the second gear stage can be determined based on the helix angle of the first gear stage.

[0040] The expression “helix angle of a gear stage” means here and hereinafter that a gear wheel involved in the respective gear stage, ie, for example, a motor gear wheel and / or an involved stepped gear wheel, comprises a helical toothing with a corresponding helix angle.

[0041] In order to realize a particularly durable and smooth-running spur gear transmission, the jump overlap of at least one helical toothing can be a non-integer. By combining mutually connected helical toothings in successive transmission stages and at least one non-integer jump overlap, a relatively small helix angle can be achieved, whereby high axial loads acting on the participating gears and / or bearing points can be avoided or at least reduced.

[0042] Rather, in this variant it is possible to set a desired load distribution or a distribution of the mechanical loads occurring within the spur gear drive by selecting the jump overlap and the resulting helix angle.

[0043] For example, the helix angle of at least one gear stage, in particular the second gear stage and each higher gear stage, is less than 10°.

[0044] In particular, the overlap of the transitions of at least one helical toothing, preferably of each helical toothing or of each helical toothing starting from the second gear stage, is less than 1.

[0045] In one variant, the helix angle of the helical toothing of the first gear stage is determined according to the following formula (2):

[0046]

[0047] Where β1 represents the helix angle of the first transmission stage, F AxM Indicates the axial force acting on the motor gear, d w1.1 represents the pitch diameter of the motor gear in the first gear stage, T M represents the driving torque acting on the motor gear, and 1 / b represents the axial force F acting on the motor gear. AxM A predetermined portion of this axial force should act on the bearing point of the first transmission stage.

[0048] By selecting a suitable factor 1 / b it is possible to determine which loads the bearing points of the first gear stage must withstand and thus how elaborately the corresponding bearing points must be designed in order to ensure adequate durability of the belt tensioner.

[0049] For example, the coefficient 1 / b may be in the range of 0.4 to 0.8, in particular in the range of 0.5 to 0.75.

[0050] In other words, for example, b is in the range of 1.25 to 2.5, in particular in the range of 1.33 to 2.0.

[0051] Preferably, the helix angle of the second transmission stage or higher transmission stages is determined according to the following formula (3):

[0052]

[0053] Where: β x represents the helix angle of the respective transmission stage x, n represents the total number of transmission stages, d wx.1 denotes the pitch diameter of the pinion in the respective transmission stage x and d w(x-1).2 Denotes the pitch circle diameter of the step gear in the upstream gear stage (x-1).

[0054] The value of b in formula (3) is determined from formula (2) by selecting the coefficient 1 / b. That is, the value of b in formula (3) is determined by the axial force F acting on the motor gear. AxM Which predetermined portion 1 / b of is to act on the bearing point of the first transmission stage is determined.

[0055] In order to prevent incorrect assembly during the production of the belt tensioner according to the modular system according to the invention, each stepped gear pair can have an optical identification means.

[0056] As an optical identification means, a unique identifier, for example a part number, a part name, a surface profile, a barcode and / or a QR code can be mounted on the stepped gear of the respective stepped gear pair.

[0057] Additionally or alternatively, a colored marking may be present as optical identification means.

[0058] In one variant, the module system comprises a plurality of electric motors operable at different voltages and / or an electric motor operable at at least two different voltages, wherein the electric motor in the belt tensioner is connected to the motor gear for driving the motor gear.

[0059] The use of an electric motor in the belt tensioner makes it possible to design the belt tensioner as a reversible belt tensioner.

[0060] In the belt tensioner, the control motor can be regulated by means of the current supplied to the motor.

[0061] For tensioning, the motor must provide high torque at high speed so that the belt can be tensioned with sufficient force and speed.

[0062] In particular, the electric motor of the module system can be operated at a voltage of 12 V and / or 48 V.

[0063] Electric motors operated at 12 V can be used in particular for applications such as reducing belt slack by targeted actuation of the belt webbing or for implementing warning functions, since relatively low shoulder forces are sufficient for these applications.

[0064] If an additional pyrotechnic component is used in the belt tensioner for full tensioning applications, a more powerful electric motor does not have to be provided. Therefore, in this case, an electric motor operating at 12V can be selected from the module system according to the invention, together with a stepped gear pair providing a suitable transmission ratio.

[0065] Such an electric motor operated at 12V can be briefly overloaded in the vehicle's 48V onboard electrical system in order to be able to provide a high force for a short period of time, for example, in order to be used additionally in a fully tensioned situation. However, this requires an increased transmission ratio in order to withstand the greater torque generated by the overloaded electric motor. This can be achieved in a simple manner by selecting a suitable stepped gear pair of the module system, without requiring additional adaptation of other components in the belt tensioner.

[0066] In this context, the term "short-term overload" refers in particular to an overload for a period of 0.5 seconds or less.

[0067] It is also possible that at least one of the motors of the module system is a motor with a rated operating voltage of 48 V, i.e., not an electric motor that is operated at 48 V only within the framework of a short-term overload. Such a motor requires a lower transmission ratio in order to generate the desired relatively low shoulder forces for applications that do not correspond to fully tensioned load conditions. In this case, too, a correspondingly designed belt tensioner can be produced in a simple manner by means of a targeted selection of a suitable stepped gear pair of the module system, without having to further adapt the components of the belt tensioner.

[0068] For each of the stepped gear pairs, the transmission ratio in the second transmission stage can be in the range of 16 to 58, in particular in the range of 24 to 46.

[0069] In other words, the modular system according to the invention makes it possible to cover a significantly wider range of transmission ratios than is the case with conventional belt tensioners, without requiring a complex redesign of the components of the belt tensioner.

[0070] In another variant, the stepped gears of the stepped gear pair are produced by means of an injection molding process and / or by means of a sintering process.

[0071] In particular, the stepped gears are manufactured as complete components, ie the gears of the respective stepped gear for both transmission stages in which the respective stepped gear participates are produced simultaneously in one production step, so that no further assembly steps are necessary.

[0072] Stepped gears manufactured by injection molding are especially made of plastic. Such stepped gears can be manufactured at a relatively low cost, but are only suitable for use under relatively low maximum torques compared to step gears made of metal or metal alloys.

[0073] In order to produce stepped gears from plastic for different stepped gear pairs in a cost-effective and flexible manner, the stepped gears can be produced from plastic by using interchangeable inserts by means of an injection mold. Thus, flexible and demand-adaptable production can be achieved by replacing the interchangeable inserts.

[0074] Stepped gears manufactured by means of a sintering process are made, in particular, of metal or a metal alloy. Compared with stepped gears made of plastic, such stepped gears are more expensive to manufacture, but are suitable for use under higher maximum torques.

[0075] The object of the invention is also achieved by a belt tensioner produced by a module system as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Further advantages and features of the invention are apparent from the following description of exemplary embodiments and from the accompanying drawings, which, however, are not to be understood in a restrictive sense. In these drawings:

[0077] Figure 1 A top view of selected parts of a belt tensioner according to a first embodiment of the invention, which is produced by means of the module system according to the invention,

[0078] Figure 2 Show Figure 1 A top view of a stepped gear transmission with a tensioner,

[0079] Figure 3 Show Figure 2 A perspective view of the components of a stepped gear transmission.

[0080] Figure 4 A top view showing a stepped gear transmission of a second embodiment of the belt tensioner according to the invention, and

[0081] Figure 5 A plan view of a stepped gear transmission showing a third embodiment of a belt tensioner according to the invention. DETAILED DESCRIPTION

[0082] exist Figure 1 Detailed Description of the Invention A first embodiment of a belt tensioner 10 according to the invention is shown, which belt tensioner can be used in a seat belt system, for example for an occupant in a vehicle.

[0083] The belt tensioner 10 is formed by a module system 11 according to the invention (see Figure 2 ) is made of.

[0084] The belt tensioner 10 is connected to a frame 12 of a belt retractor 14 , in which a belt reel 16 is rotatably mounted in order to wind up a belt webbing (not shown) and to eliminate belt slack, for example when the belt retractor 14 is triggered.

[0085] The belt tensioner 10 has a spur gear 18 which is accommodated in a housing 20 . The housing 20 comprises an underside 22 of the housing 20 and a housing cover 24 .

[0086] exist Figure 2 Shown in Figure 1 A top view of a spur gear transmission 18 used in the belt tensioner 10 in FIG.

[0087] The spur gear 18 is accommodated in its installed position in a housing 20 of the belt tensioner 10 (see Figure 1 ), the module system 11 comprises housings 20 of identical design, in each of which a spur gear 18 can be inserted.

[0088] from Figure 2 It can be seen that the spur gear 18 has a motor gear 26 (also called motor pinion), a first stepped gear 28 , a second stepped gear 30 and a third stepped gear 32 .

[0089] The motor gear 26 and the first stepped gear 28 form a first transmission stage 34 , the first stepped gear 28 and the second stepped gear 30 form a second transmission stage 36 , and the second stepped gear 30 and the third stepped gear 32 form a third transmission stage 38 .

[0090] It is understandable that the module system 11 can also be provided with only the first transmission stage 34 and the second transmission stage 36 or also with more than three transmission stages.

[0091] In the embodiment shown, the motor gear 26 , the first stepped gear 28 , the second stepped gear 30 and the third stepped gear 32 are produced from plastic by means of an injection molding process.

[0092] In principle, the motor gear 26 , the first stepped gear 28 , the second stepped gear 30 and / or the third stepped gear 32 can also be made of metal or a metal alloy and produced, for example, by means of a sintering method.

[0093] The motor gear 26 is driven by means of an electric motor 40 (only indicated schematically), wherein the motor gear 26 can be driven clockwise or counterclockwise. In other words, the belt tensioner 10 shown is a reversible belt tensioner.

[0094] The module system 11 has a plurality of electric motors 40 which can be operated at different voltages.

[0095] The electric motor 40 of the first embodiment of the belt tensioner 10 is an electric motor designed for an operating voltage of 12 V. For example, the operating voltage is provided via an onboard power supply of a vehicle (not shown) in which the belt tensioner 10 is installed.

[0096] All gears involved in the spur gear transmission 18 , namely the motor gear 26 , the first stepped gear 28 , the second stepped gear 30 and the third stepped gear 32 , have an opening 42 extending axially through the respective gear.

[0097] Arranged in each of these openings 42 is a shaft 44 which matches a corresponding gear wheel.

[0098] The distance between the axles 44, also called the wheelbase, is Figure 2 In the figure, they are respectively represented as a1, a2 and a3, wherein the wheelbase a1 represents the distance between the axis 44 of the motor gear 26 and the axis of the first step gear 28, the wheelbase a2 represents the distance between the axis 44 of the first step gear 28 and the axis of the second step gear 30, and the wheelbase a3 represents the distance between the axis 44 of the second step gear 30 and the axis of the third step gear 32.

[0099] In addition, Figure 2 2 , a wheelbase a4 is shown, which indicates the distance between the shaft 44 of the third stepped gear 32 and the retracting shaft 46 of the belt retractor 14 .

[0100] The first stepped gear 28 and the second stepped gear 30 form a stepped gear pair of the module system 11 according to the invention, wherein the module system 11 comprises a plurality of stepped gear pairs.

[0101] For each of the stepped gear pairs, the number of teeth of the first stepped gear 28 and the number of teeth of the second stepped gear 30 are different from those of the other stepped gear pairs, while the wheelbase a2 is the same for each of the stepped gear pairs.

[0102] Furthermore, in the illustrated embodiment, the sum of the number of teeth of the first stepped gear 28 and the second stepped gear 30 in the second gear stage 36 is the same for each stepped gear pair therein.

[0103] In principle, however, the number of teeth between different step gear pairs can also be different, as long as the resulting axial distance can continue to be designed to be constant. This can also be achieved, for example, by selecting the helix angle, the normal module or the tooth profile modification factor.

[0104] The overall transmission ratio of the stepped gear transmission 18 results as the product of the intermediate transmission ratios of all transmission steps and of the transmission step between the last stepped gear and the belt retractor 14 , ie, in the embodiment shown, between the third stepped gear 32 and the belt retractor 14 .

[0105] For example, a spur gear transmission has an overall transmission ratio of 32.

[0106] The modular system 11 according to the invention makes it possible to adapt and determine the overall transmission ratio of the spur gear 18 simply by changing the stepped gear pairs used, namely in the embodiment shown via the selection of the number of teeth of the first stepped gear 28 and the second stepped gear 30 in the second transmission stage 36 .

[0107] The wheelbases a1 to a4 can therefore remain constant for each selected stepped gear pair, so that other components of the belt tensioner 10 do not have to be adapted when the overall transmission ratio of the spur gear 18 is to be adapted.

[0108] exist Figure 3 Shown in Figure 1 1 is a perspective view of selected parts of the spur gear 18 in FIG.

[0109] In this view, the shafts 44 that axially pass through the first step gear 28 and the second step gear 30 can be more Figure 2 It can also be seen more clearly in FIG. It can also be seen that each shaft 44 transitions into a collar-shaped projection 48 at the axial lower end, which is in contact with the (not shown in detail) bearing position of the lower side 22 of the housing 20 (see FIG. Figure 1 )match.

[0110] exist Figure 3 It can also be seen that the motor gear 26 , the first stepped gear 28 and the second stepped gear 30 have helical toothing.

[0111] Helical toothing allows for improved running smoothness and, by selecting the jump overlap or the helix angle of the helical toothing, a desired load distribution at the bearing points of the respective gear wheel can be achieved.

[0112] It can also be seen that the first transmission stage 34 is closer to the underside 22 of the housing 20 than the second transmission stage 36 (see FIG. Figure 1 ) arrangement.

[0113] Figure 4 The diagram shows a plan view of a stepped gear 18 of a second specific embodiment of a belt tensioner 10 which is produced using the module system 11 according to the invention.

[0114] The second embodiment corresponds substantially to the first embodiment, so only the differences are discussed below. The same reference numerals denote the same components and reference is made to the previous description.

[0115] In the second embodiment, the first stepped gear 28 in the second transmission stage 36 has a smaller number of teeth than in the first embodiment, and the second stepped gear 30 in the second transmission stage 36 has a larger number of teeth. In other words, a different stepped gear pair is selected during the production of the belt tensioner 10 than for the first embodiment.

[0116] However, the other components of the stepped gear transmission 18 remain unchanged, in particular the transmission ratios in the first transmission stage 34 , in the third transmission stage 38 and between the third stepped gear 32 and the belt retractor 14 are the same.

[0117] Therefore, the belt tensioner 10 of the second embodiment has a higher overall transmission ratio than that of the first embodiment, for example, the overall transmission ratio is 46.

[0118] The wheelbase between the participating gearwheels is identical to the first embodiment of the belt tensioner 10 , so that no adaptation of the housing 20 is necessary.

[0119] In the second embodiment, the second stepped gear 30 additionally has an optical identification means 50 in order to avoid confusion with other second stepped gears 30 of the module system 11. In the embodiment shown, the optical identification means 50 is a barcode.

[0120] In principle, however, other unique identifiers can also be used as optical identification means 50 , such as a part number, a part name, a surface contour, a QR code and / or a color code.

[0121] Due to the high gear ratio, the belt tensioner, when using an electric motor 40 running at 12V, is suitable for use in seat belt systems which should enable vehicle occupant repositioning.

[0122] Alternatively, a motor 40 of the module system 11 can be additionally operated at 48 V, for example by briefly overloading the motor 40. In this case, the belt webbing can be fully tensioned due to the high transmission ratio of the belt tensioner 10, so that the use of additional pyrotechnic components can be omitted.

[0123] Figure 5 The diagram shows a plan view of a stepped gear 18 of a third embodiment of a belt tensioner 10 which is produced using the module system 11 according to the invention.

[0124] The third embodiment corresponds substantially to the first and second embodiments, so only the differences are discussed below. The same reference numerals denote the same components and reference is made to the previous description.

[0125] In the third embodiment, the first stepped gear 28 in the second transmission stage 36 has a greater number of teeth and the second stepped gear 30 in the second transmission stage 36 has a smaller number of teeth than in the first embodiment. In other words, different stepped gear pairs are selected during the production of the belt tensioner 10 for the first and second embodiments.

[0126] However, apart from the electric motor 40 , the other components of the stepped gear transmission 18 remain unchanged, in particular the transmission ratios in the first transmission stage 34 , in the third transmission stage 38 and between the third stepped gear 32 and the belt retractor 14 are identical.

[0127] Therefore, the belt tensioner 10 of the third embodiment has a smaller total transmission ratio than that of the first embodiment, for example, a total transmission ratio of 24.

[0128] The wheelbase between the participating gearwheels is identical to the first and second embodiments of the belt tensioner 10 , so that no adaptation of the housing 20 is necessary either.

[0129] Due to the smaller transmission ratio, the belt tensioner 10 of the third embodiment is suitable for use with an electric motor 40 designed for operation at a voltage of 48 V, i.e., can generate a greater torque than an electric motor designed for operation at 12 V. The smaller overall transmission ratio enables the belt tensioner 10 to still be used for applications where only small forces have to be generated, such as reducing belt slack, while the same belt tensioner 10 can also be used for applications where large forces have to be generated, such as full tensioning. In other words, the belt tensioner 10 of the third embodiment makes the use of pyrotechnic components superfluous.

[0130] The modular system 11 according to the invention enables the production of different belt tensioners 10 with little effort, which are suitable for different desired application scenarios.

[0131] In particular, in the current production process, only those first step gears 28 and second step gears 30 having the exact required number of teeth need to be manufactured, while the other components of the belt tensioner 10 can remain unchanged. Thus, flexible and demand-compliant production of the belt tensioner 10 can be achieved.

Claims

1. A modular system with a spur gear transmission (18) for a belt tensioner (10), wherein: The cylindrical gear transmission (18) comprises at least one motor gear (26) and at least one first step gear (28) and a second step gear (30), wherein the motor gear (26) and the first step gear (28) form a first transmission stage (34) and the first step gear (28) and the second step gear (30) form a second transmission stage (36), The module system (11) comprises a plurality of stepped gear pairs consisting of a first stepped gear (28) and a second stepped gear (30), The module system (11) comprises housings (20) of identical design, in each of which a spur gear transmission (18) with one of the stepped gear pairs can be installed. Each first stepped gear (28) and each second stepped gear (30) has an opening (42) extending axially through the respective stepped gear (28, 30) for receiving a shaft (44), wherein each shaft (44) is provided with a bearing point of the housing (20), and For each of the stepped gear pairs, the number of teeth of the first stepped gear (28) and the number of teeth of the second stepped gear (30) are different from the number of teeth of the other stepped gear pairs, but the distance between the axis (44) of the first stepped gear (28) and the axis (44) of the second stepped gear (30) is the same for each of the stepped gear pairs.

2. The modular system according to claim 1, wherein: The sum of the number of teeth of the first step gear (28) and the second step gear (30) in the second transmission stage (36) is the same for each step gear pair.

3. The modular system according to claim 1 or 2, wherein: Each gear (26, 28, 30, 32) used in the belt tensioner (10) has an opening (42) axially extending through the respective gear (26, 28, 30, 32) for receiving a shaft (44), and each shaft (44) is provided with a bearing point of the housing (20), and each distance between every two shafts (44) is the same for each stepped gear pair.

4. The modular system according to claim 1, wherein: The first transmission stage (34) is arranged closer to the underside (22) of the housing (20) than the second transmission stage (36).

5. The modular system according to claim 1, wherein: The dimensions of the housing (20) of identical design are adapted to accommodate the stepped gear pairs that are most demanding in terms of installation space.

6. The modular system according to claim 1, wherein: At least two mutually meshing gears (26, 28, 30, 32) of the spur gear transmission (18), in particular a first stepped gear (28) and a second stepped gear (30), have helical toothing.

7. The modular system according to claim 1, wherein: Each stepped gear pair includes an optical identification device (50).

8. The modular system according to claim 1, wherein: The module system (11) comprises a plurality of electric motors (40) which can be operated at different voltages and / or an electric motor (40) which can be operated at at least two different voltages, wherein the electric motor (40) is connected to the motor gear (26) in the belt tensioner for driving the motor gear (26).

9. The modular system according to claim 1, wherein: The stepped gears (28, 30) of the stepped gear pair are produced by means of an injection molding process and / or by means of a sintering process.

10. Belt tensioner produced by a module system (11) according to one of the preceding claims.

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