GURTAUFROLLER

Description

[0001] The present invention relates to a belt retractor having the features of the preamble of claim 1.

[0002] Belt retractors consist of a load-bearing frame and a belt reel mounted rotatably within the frame, onto which a seat belt can be wound. In addition to supporting the belt reel, the frame also serves as a mounting point for attachment to a seat structure or vehicle structure. For this purpose, it is made of a suitably thick sheet steel bent into a U-shaped frame.

[0003] Furthermore, belt retractors in modern safety belt systems are equipped with electric motors which, when activated, drive the belt shaft in the winding direction, for example for reversible belt tensioning. The electric motor is also attached to the frame and arranged to the side of the belt shaft with a drive shaft aligned parallel to the axis of rotation of the belt shaft. It is also known to provide a gearbox between the belt shaft and the electric motor, by means of which the speed of the electric motor is translated into a predetermined speed of the belt shaft. The use of the gearbox also makes it possible to use the smallest possible electric motor with a high speed. Overall, this results in a belt retractor with increased installation space requirements, despite the use of the compact electric motor made possible by the gearbox. Such a belt retractor is known, for example, from the document WO 03 / 0 99 619 A2.

[0004] If the belt shaft is to be driven at different speeds and torques, additional gear stages must be provided, which further increases the installation space required. Such a belt retractor is known, for example, from document DE 199 27 731 C2.

[0005] Since the installation space available on the seat structure of the vehicle seats or generally in very small vehicles is very limited in size and cannot be enlarged at will for design reasons, the arrangement of such a belt retractor on the vehicle seat or even in a small vehicle is fundamentally problematic.

[0006] DE 10 2018 219 040 A1 discloses a belt retractor in which the installation space requirement is further reduced by driving the transmission as an assembly in a first power transmission path, and by providing a clutch which activates the transmission through a switching operation and opens a second power transmission path. This allows a transmission with a single power transmission path to be used to implement two different gear ratios. The transmission itself is driven as an assembly in the first power transmission path, i.e. as a block, without the transmission parts moving relative to one another. The clutch here has a drive wheel driven by the electric motor with three triangular openings that narrow radially outwards, into which a clutch pawl with a control pin engages.The clutch pawls are longitudinally movable, guided radially, and each spring-loaded radially outward. To engage the clutch, the clutch pawls are pulled radially inward against the spring force when a certain rotational acceleration of the drive wheel is exceeded, thereby breaking the rotary connection between the clutch pawls and a first part associated with the transmission.

[0007] Against this background, the object of the invention is to provide an improved belt retractor with an electric motor and a transmission with a clutch with a simplified structure.

[0008] To achieve this object, a belt retractor having the features of claim 1 is proposed. Further preferred developments of the invention can be found in the subclaims, the figures, and the associated description.

[0009] According to the basic idea of ​​the invention, it is proposed according to claim 1 that the coupling element is mounted on a second part of the transmission, and the second part has a rotationally fixed gear with which it is in meshing engagement with one or more gears of a transmission gear, and the spring is formed by a bow spring which is connected at a first end to the coupling element and at a second end to the second part.

[0010] The second part of the gear, on which the clutch element is mounted, simultaneously forms the drive via the non-rotatably connected gear, through which the rotary motion is transmitted to the transmission gear. The advantages of using a bow spring are that it is cost-effective, easy to install, and can also be very easily connected to the clutch element and the second part in a force-transmitting manner, for example, through openings or stop surfaces.

[0011] It is further proposed that the clutch element transmit the rotational movement of the drive wheel to the first part of the transmission at low torques, speeds, and / or rotational accelerations. This allows the rotational movement of the electric motor, at low torques, speeds, and / or rotational accelerations, to be transmitted directly via the clutch element to the first part of the transmission in a first power transmission path, e.g., to the belt shaft at a transmission ratio of 1:1. This allows, for example, a winding aid for the seat belt into the parking position, a comfort function for adjusting the retraction force acting on the belt shaft, or similar functions to be implemented.

[0012] The clutch element can preferably have an engagement section engaging the first part of the transmission, and the clutch element can have at least two force-transmitting sections symmetrically formed with respect to an axis of symmetry extending through the engagement section, with which the clutch element bears against the polygonal force-transmitting profile of the drive gear. The clutch element transmits the rotational movement via the engagement section to the first part. Due to the symmetrical force-transmitting sections, the power is transmitted from the drive gear to the clutch element in both directions of rotation with force ratios that are as identical as possible, and the clutch element can be mounted in two different orientations.

[0013] It is further proposed that the polygonal power transmission profile has a triangular profile in cross-section, and that the coupling element encompasses the triangular profile at two corners. The coupling element encompasses the power transmission profile at two corners with a positive overlap, thereby transmitting the drive rotation in both directions of rotation. Furthermore, if one of the predetermined conditions is exceeded, the coupling element is positively engaged and pulled out of the engaged position.

[0014] Symmetrical power transmission with force ratios as identical as possible in both directions of rotation can preferably be achieved by designing the triangular profile with the geometry of an equilateral triangle. Furthermore, this can simplify installation, as the belt retractor can be installed with the drive wheel in three different positions. Since the vertices of the triangular profile thus have an identical geometry, it is particularly irrelevant which of the vertices the coupling element with the power transmission section(s) rests against.

[0015] It is further proposed that in this case, the second part has a stop surface against which the drive wheel with the power transmission profile comes into contact in a force-transmitting manner by executing a relative movement. The relative movement is triggered when the predetermined speed, the predetermined torque, and / or the predetermined rotational acceleration are exceeded. As a result, the coupling element is moved out of the engaged position, and the drive wheel comes into force-transmitting contact with the second part. As a result, the drive wheel drives the second part and, via the gearwheel connected to it in a rotationally fixed manner, also the transmission gear, while the rotary connection between the drive wheel and the first part is simultaneously released.

[0016] The second part can preferably have a guide in which the coupling element is guided with the engagement section. The movement of the coupling element is triggered by the spring force and the movement of the drive wheel, while the direction of movement is defined by the guidance of the coupling element on the second part. Guiding the coupling element in the region of the engagement section is particularly advantageous, since the coupling element is thereby preferably guided as close as possible to the connection to be made with the first part and is supported there.

[0017] The invention will be explained below using preferred embodiments with reference to the attached figures. Fig. 1 an inventive belt retractor with two housing shells assembled and disassembled Fig. 2a gearbox, an electric motor and a clutch of the belt retractor arranged in between in an exploded view Fig. 3 a sectional view with the coupling in a first position, and Fig. 4 a sectional view with the clutch in a second position.

[0018] In the Figure 1 A belt retractor 1 according to the invention with a housing composed of two housing shells 2 and 3 can be seen, which serves both for fastening the belt retractor 1 to a vehicle, preferably in a narrow, elongated installation space of a vehicle seat, and for storing and fastening the individual parts of the belt retractor 1, which are described in more detail below. The housing can also be part of a higher-level structure of the vehicle seat or the vehicle, such as a strut or a spar.

[0019] The housing is provided on the inside with several webs 24 for supporting the belt retractor 1, which webs are aligned perpendicular to the axis of rotation of the belt retractor and are connected to the housing in a form-fitting and rotationally fixed manner with respect to the axis of rotation. The belt retractor 1 has, as its basic component, a belt shaft 4, onto which a safety belt intended to restrain an occupant can be wound. Furthermore, an irreversible belt tensioner 7 is provided for driving the belt shaft 4 in the winding direction and thus for removing any slack in the belt in the early phase of an accident. An electric motor 5 and a gear 6 are also provided. The belt shaft 4, the irreversible belt tensioner 7, the electric motor 5 and the gear 6 are arranged coaxially with one another.Furthermore, the external dimensions of the electric motor 5, the gear 6, and the irreversible belt tensioner 7 perpendicular to the rotational axis of the belt shaft are dimensioned such that they are smaller than the maximum diameter of the fully wound belt reel on the belt shaft 4. Since the housing has a square cross-section, additional free space remains in the corners, which can be used, for example, to accommodate a tensioner drive tube of the irreversible belt tensioner 7 or other add-on components, such as control units or electrical cables. The maximum external dimensions are thus determined by the maximum diameter of the belt reel.Since the maximum diameter is in turn determined by the thickness of the belt webbing and the maximum length of the belt webbing to be wound up and cannot be reduced without changing the belt webbing, the belt retractor 1 thus has the smallest possible dimensions perpendicular to the axis of rotation of the belt shaft 4 and can therefore also be arranged and fastened in very narrow and elongated free spaces of the vehicle seat and the vehicle structure.

[0020] In the Figure 2 the electric motor 5 is shown with the gearbox 6, a clutch 8 arranged therebetween and an additionally provided optional force limiting unit 11.

[0021] The transmission 6 comprises the clutch 8, a transmission gear 9, which is designed here as a planetary gear, and a transmission housing 10 as its basic components. The transmission 6 is enclosed externally by the transmission housing 10 and has a cylindrical basic shape. The transmission housing 10 itself is tubular or ring-shaped and has internal gearing on its inside, in which the planetary gears of the planetary gear roll.

[0022] The electric motor 5 has a protruding drive shaft 18, on which a drive gear 17 is fixedly mounted via a toothed mesh. The electric motor 8 thus directly drives the drive gear 17 upon activation.

[0023] The basic structure of the clutch 8 comprises a first part 13, a second part 14, a clutch element 15, and a spring 12. The first part 13 is in the form of a ring with a regular tooth profile 30 arranged radially on the inside. Furthermore, the first part 13 has a plurality of recesses on the radial outside, which are aligned with recesses in the transmission housing 10. The first part 13 is covered on the front side by a cover plate 16, which additionally has axially projecting fingers with which it engages in the radially outer recesses of the first part 13 and the transmission housing 10, thereby fixing the first part 13 in a rotationally fixed manner relative to the transmission housing 10 in the circumferential direction. If the connection is realized via a press fit, this can additionally axially secure the first part 13 relative to the transmission housing 10.The first part 13 has a circular free space radially inward, in which the second part 14 of the coupling 8 is rotatably arranged, as also in the . Figures 3 and 4 can be seen. Thus, after the cover plate 16 has been placed in place, the second part 14 is also axially fixed. The cover plate 16 further has a central opening through which the drive wheel 17 extends. The drive wheel 17 has a polygonal force transmission profile 19 at its free end, with which it engages in a free space provided radially on the inside of the second part 14. Furthermore, the coupling element 15 is arranged in the free space of the second part 14 such that it encompasses the force transmission profile 19 radially on the outside.

[0024] The polygonal power transmission profile 19 of the drive wheel 17 has the geometry of an equilateral triangle with three corners 27, 28, and 29 with identical angles and thus identically aligned lateral power transmission surfaces. The coupling element 15 has a radially projecting engagement section 22, with which it is guided radially displaceably in a guide 32 of the second part 14. Furthermore, the coupling element 15 has two arcuate arms symmetrically formed with respect to an axis of symmetry S running through the center of the engagement section 22, which complement each other approximately to form a semicircle. At the ends of the arms, the coupling element 15 is each formed with radially inwardly directed power transmission sections 20, 21, with which it encompasses a respective corner 28, 29 of the power transmission profile 19 of the drive shaft 17, as shown in the Figure 3can be seen. The spring 12 is in the form of a bow spring and is suspended with a first end 25 on the coupling element 15 in an opening arranged radially inwards towards the engagement section 22, on the axis of symmetry S. Furthermore, the spring 12 is suspended with a second end 23 in an opening in the second part 14, which is arranged such that in the unloaded arrangement of the coupling element 15, i.e. when the electric motor 5 is at a standstill, it also lies on the axis of symmetry S. The spring 12 is designed in its spring characteristics and in the arrangement of the two fixed ends 25 and 23 such that it urges the coupling element 15 with the engagement section 22 radially outwards into engagement with the tooth profile 30 of the first part 13. As a result, a rotary connection between the first part 13 and the second part 14 is created by the coupling element 15 in the unloaded state.

[0025] In the event that the electric motor 5 in the Figure 3to be recognized initial position of the coupling element 15 with small torques, speeds and / or rotational accelerations, as is the case, for example, for winding up the safety belt into the parking position or for adjusting the retraction force exerted on the belt shaft 4 (comfort function), the drive wheel 17 drives the first part 13 via the power transmission profile 19 and the coupling element 15. Since the first part 13 is connected to the gear housing 10 in a rotationally fixed manner via the cover plate 16, the entire gear 6 is driven as an assembly and, via it, the belt shaft 4 in a transmission ratio of 1:1. The belt shaft 4 can be driven via the two power transmission sections 20, 21 in both directions of rotation, whereby the power is transmitted only via one of the power transmission sections 20 or 21 depending on the direction of rotation. Since both the coupling element 15 and the power transmission profile 19 are in the position of Figure 3 are aligned symmetrically to the axis of symmetry S, identical force ratios result in both directions of rotation. The second part 14 has a centrally arranged gear 31 on its axial end face facing the planetary gear system, which engages with the toothing of the planetary gears of the planetary gear system. Since the second part 14 rotates at an identical speed to the first part 13, the entire gear system 6 is also driven via the central gear 31. The entire gear system 6 rotates together with the first part 13 and the second part 14 as an assembly at the speed driven by the drive shaft 17, without the gears of the gear system 6 performing any further relative rotational movements to one another.

[0026] The clutch 8 is opened by increasing the power of the electric motor 5, e.g., for reversible belt tensioning, to such an extent that a predetermined speed, a predetermined torque and / or a predetermined rotational acceleration is exceeded. In this case, the drive wheel 17 rotates so fast that the clutch element 15 remains behind and, against the spring force of the spring 12, is moved into the position defined in the Figure 4to be recognized. In doing so, the coupling element 15 with the engagement section 22 disengages from the toothed profile 30, and the rotary connection between the first part 13 and the second part 14 is released. The coupling 8 is thus opened. At the same time, the drive shaft 17, with a side surface of the power transmission profile 19, comes into contact with a stop surface 26 of the second part 14 and thereby subsequently drives the second part 14 directly in a rotary movement, while the first part 13 is no longer driven due to the opened coupling 8.

[0027] In this case, the rotational movement of the second part 14 is transmitted via the central gear 31 to the gears of the planetary gear. The gear housing 10 is no longer driven and can additionally be locked to the vehicle via a blocking device 33. In any case, the gears of the planetary gear rotate relative to the gear housing 10, and the rotational movement of the drive shaft 17 is now translated into a slower speed on the belt shaft 4 at a transmission ratio of 1:80. Due to the translation of the higher speed into the lower speed, the torque exerted on the belt shaft 4 and the resulting retraction force on the seat belt are simultaneously increased.

[0028] The electric motor 5 can thus be operated in a first power transmission path with the clutch 8 engaged and the gearbox 6 deactivated at a gear ratio of 1:1 and a speed of 60 to 180 rpm for winding up the belt webbing after unbuckling into the parking position by rotating the gearbox 6 as a block. If the proposed speed is also to be the speed of the belt shaft 4, the drive rotational movement can then also be transmitted to the belt shaft 4 at a gear ratio of 1:1. For reversible belt tensioning, the speed of the electric motor 5 can be suddenly increased to 5,000 to 15,000 rpm, which is translated by the gearbox 6 in the second power transmission path opened up by the disengaged clutch 8 to the lower speed of approximately 140 to 420 rpm of the output gear 23 at a gear ratio of 1:80.To engage clutch 8, the significantly higher drive speed of 5,000 to 15,000 rpm is used compared to the drive speed of 60 to 180 rpm when driving belt shaft 4 in the first power transmission path. Thus, clutch 8 or the transmission 6 with integrated clutch 8 can be designed so that it only opens when, for example, the drive speed exceeds 1,000 rpm.

[0029] This ensures reliable transmission of the drive rotational movement from 60 to 180 rpm in the first power transmission path, and prevents unintentional opening of clutch 8 during the winding process of the seat belt into the parking position. Furthermore, as an alternative to speed-controlled opening, clutch 8 can also open if the torque to be overcome suddenly increases at the same or decreasing speed. Such a situation can arise, for example, if the seat belt is wound into the parking position at high speed. When the seat belt is then almost completely wound, the torque to be overcome increases, and clutch 8 engages automatically.By switching the clutch 8, the speed of the output gear 23 is reduced and the torque exerted by the output gear 23 is increased, so that the safety belt is subsequently wound up with a lower retraction speed and an increased retraction force.

[0030] The transmission 6 has a single power transmission path through the planetary gearing, in this case a two-stage planetary gearing. The proposed solution for transmitting the drive rotational movement via the transmission 6 rotating as an assembly creates a first power transmission path for implementing a first function—here, winding the seat belt into the parking position—without requiring additional installation space. Furthermore, the clutch 8 is engaged very simply by increasing the speed, so that the second power transmission path is automatically opened when the speed of the electric motor 5 is increased to tighten the seat belt—i.e., for its second function. The engagement of the clutch 8 is thus directly controlled by the change in function of the electric motor 5 itself.

[0031] Furthermore, the electric motor 5 and the gear 6 are cylindrical and aligned coaxially to one another and coaxially to the axis of rotation of the belt shaft 4. Furthermore, both the electric motor 5 and the gear 6 have a diameter in cross-section to their axis of rotation that is smaller than the outer diameter of the belt reel when the belt is fully wound up. This results in a very slim, elongated design of the belt retractor, the maximum outer dimensions of which are predetermined by the maximum outer diameter of the belt reel. Since the maximum outer diameter of the belt reel is mandatory due to the thickness and length of the belt to be wound up and cannot be reduced, the belt retractor can thus be designed with the smallest possible dimensions perpendicular to the axis of rotation of the belt shaft 4.

[0032] The clutch 8 is understood here as an assembly of the transmission 6, so that the first part 13 and the second part 14 are, of course, parts of the clutch 8 but thus also parts of the higher-level assembly of the transmission 6. For this purpose, the clutch 8 is preferably arranged on the input side of the transmission 6 facing the electric motor 5.

[0033] The electric motor 5 is preferably voltage-controlled and, by applying different voltages, causes different torques acting on the belt shaft 4 or different retraction forces exerted on the seat belt. When the seat belt is normally worn, a voltage of 2 to 3 V is applied, which reduces the retraction force to the lowest possible level, but is still sufficient to reliably pull the seat belt towards the occupant after the occupant moves. To wind the seat belt into the parking position after unbuckling, the voltage is increased to 9 V, so that the seat belt is wound into the parking position with an increased retraction force. Furthermore, the voltage is also increased to 12 V during a reversible tensioning process, which is sufficient for a possibly additionally provided function of reversible belt tensioning with an increased retraction force of approx.36 V can be increased.

Claims

1. Belt retractor (1) comprising - a belt shaft (4) which is rotatably mounted in a housing and onto which a seat belt can be wound, the housing being able to be fastened to the vehicle, and - an electric motor (5) for driving the belt shaft (4) to move rotationally, and - a gear mechanism (6) which transmits the rotational movement from the electric motor (5) to the belt shaft (4), - the gear mechanism (6) being able to be driven in a first force-transmission path as an assembly to drive the belt shaft (4) with a first torque, and - the gear mechanism (6) being able to be driven to drive the belt shaft (4) with a second torque, by shifting a speed-controlled and / or torque-controlled coupling (8), whereby a second force-transmission path is opened, - the coupling (8) having at least one coupling element (15) which is springloaded by a spring (12) into engagement in a first part (13) of the gear mechanism (6), - a drive wheel (17) which is connected to the electric motor (5) for conjoint rotation and has a polygonal force-transmission profile (19) being provided, and - the coupling element (15) having at least one force-transmission portion (20,21) which abuts the polygonal force-transmission profile (19) and by which the coupling element (15) can be moved, against the force of the spring (12), out of engagement in the first part (13) of the gear mechanism (6) due to a relative movement of the drive wheel (17) relative to the coupling element (15) when a predetermined rotational speed transmitted by the drive wheel (17) and / or a predetermined torque and / or a predetermined rotational acceleration is exceeded, and - the coupling element (15) being mounted on a second part (14) of the gear mechanism (6), and - the second part (14) having a gear wheel (31) connected for conjoint rotation, with which it is in toothed engagement with one or more gear wheels of a transmission gear mechanism (9), characterized in that - the spring (12) is formed by a bow spring which is connected with a first end (25) to the coupling element (15) and with a second end (23) to the second part (14).

2. Belt retractor (1) according to claim 1, characterized in that - the coupling element (15) transmits to the first part (13) of the gear mechanism (6) the rotational movement of the drive wheel (17) below the predetermined rotational speed and / or below the predetermined torque.

3. Belt retractor (1) according to any of claims 1 or 2, characterized in that - the coupling element (15) has an engagement portion (22) engaging in the first part (13) of the gear mechanism (6), and - the coupling element (15) has at least two force-transmission portions (20,21) which are symmetrical to an axis of symmetry (S) extending through the engagement portion (22) and with which the coupling element (15) abuts the polygonal force-transmission profile (19) of the drive wheel (17).

4. Belt retractor (1) according to any of the preceding claims, characterized in that - the cross-section of the polygonal force-transmission profile (19) has a triangular profile, and - the coupling element (15) encompasses the triangular profile at two corners (27,28,29).

5. Belt retractor (1) according to claim 4, characterized in that - the triangular profile has the geometry of an equilateral triangle.

6. Belt retractor (1) according to any of claims 1 to 5, characterized in that - the second part (14) has a stop surface (26) which the drive wheel (17) with the force-transmission profile (19) comes to abut in a force-transmitting manner by the execution of the relative movement.

7. Belt retractor (1) according to any of claims 1 to 6, characterized in that - the second part (14) has a guide (32) in which the coupling element (15) is guided with the engagement portion (22).