Toothed link chain for transmitting tensile and compressive forces and drive device having such a toothed link chain

Abstract

The invention relates to a toothed link chain (2) for transmitting tensile and compressive forces in the longitudinal direction thereof and to a drive device (1) having such a toothed link chain. The toothed link chain has chain links (11, 11') which make contact in rotationally articulated fashion and which each form a chain tooth (6) rising in the transverse direction of the chain and through which an opening (12) passes in the longitudinal direction of the chain, and a tension strand (10) on which the chain links are threaded by way of their openings. The longitudinal direction of the chain and the transverse direction of the chain span a plane of curvature in which the toothed link chain curves in both directions of curvature during operation, the operational curvature of the toothed link chain in the one direction of curvature facing away from the chain teeth being limited by mutual contact of the chain links outside the rotary joints (13) thereof.

Description

[0001] Toothed link chain for transmitting tensile and compressive forces, and drive device with such a toothed link chain

[0002] The invention relates to a toothed chain with chain links that contact each other via a pivot joint, each link forming a chain tooth that rises in the transverse direction of the chain, and to a drive device with such a toothed chain. The drive device is, in particular, part of a door drive for opening and closing a motor vehicle door.

[0003] A toothed link chain of this type is known from DE 100 16698 A1. This chain can only transmit tensile forces as a power transmission element.

[0004] Autonomous, i.e., driverless, vehicles must be able to perform the entire opening and closing process of their doors without manual intervention. Without a door mechanism also known as a "smart door," they would be unable to continue their journey if a passenger left the door open after getting in or out. Therefore, smart doors are a prerequisite for fully autonomous driving. To make a vehicle door "smart" in this sense, appropriate door actuators are required. These actuators use a drive motor to operate a force transmission element that is attached between the door and a fixed point on the vehicle body, fully opening and closing the door.

[0005] Such a power transmission element can be a toothed belt capable of transmitting both tensile and compressive forces, as proposed in the unpublished German application with file number 102023 124237.7.

[0006] The present invention is based on the objective of constructively adapting a power transmission element of the type mentioned at the outset to the specific needs of power transmission and of providing a drive device with such a power transmission element.

[0007] The solution to this problem with respect to the toothed link chain is achieved by the fact that it transmits both tensile and compressive forces in its longitudinal direction and the chain links are penetrated by an opening in the chain's longitudinal direction, the toothed link chain having a tensile strand on which the chain links with their openings are threaded, the chain's longitudinal and transverse directions define a plane of curvature in which the toothed link chain bends operationally in both directions of curvature, and the operational curvature of the toothed link chain in the direction of curvature away from the chain teeth is limited by mutual contact of the chain links outside their pivot joints.

[0008] In operation, the proposed toothed chain transmits not only tensile but also compressive forces. Tensile force transmission occurs via the tension member, which holds the chain links in pivotal contact. Compressive force transmission occurs via the pressure contact of the chain links, whereby uncontrolled buckling of the chain, i.e., excessive chain curvature, is prevented by the pressure contact of the chain links, which limits the chain's curvature during operation.

[0009] The solution to this problem with regard to the drive device is achieved by comprising, as a power transmission element, such a toothed link chain, a sprocket that drives the toothed link chain with an external toothing engaging with the chain teeth in both longitudinal directions of the chain, and a chain support that contacts the chain back of the toothed link chain facing away from the chain teeth and supports the drive forces of the sprocket acting in the transverse direction of the chain.

[0010] Advantageous embodiments of the invention are the subject of the dependent claims.

[0011] Further features of the invention will become apparent from the following description and the figures, which illustrate exemplary embodiments of toothed link chains according to the invention or a drive device with such toothed link chains for operating the door of a motor vehicle. Unless otherwise stated, identical or functionally equivalent components or features are designated with the same reference numerals. The figures show:

[0012] Figure 1: a simplified representation of a section of the drive device;

[0013] Figure 2: a pair of adjacent chain links from Figure 1 as the first variant of the toothed link chain;

[0014] Figure 3: a pair of adjacent chain links as a second variant of the toothed chain;

[0015] Figure 4: a pair of adjacent chain links as the third variant of the toothed link chain;

[0016] Figure 5: a pair of adjacent chain links as the fourth variant of the toothed link chain;

[0017] Figure 6: a pair of adjacent chain links as the fifth variant of the toothed link chain;

[0018] Figure 7: a chain link with an elongated opening for the tensile cord;

[0019] Figure 8: a chain link of another chain variant with needles as a pivot joint in perspective explosion;

[0020] Figure 9: a section of the tooth link chain according to Figure 8 in perspective longitudinal section;

[0021] Figure 10: a pair of adjacent chain links as another variant of the toothed link chain;

[0022] Figure 11: a pair of adjacent chain links as another variant of the toothed link chain;

[0023] Figure 12: a pair of adjacent chain links as another variant of the toothed chain;

[0024] Figure 13: a pair of adjacent chain links as another variant of the toothed link chain;

[0025] Figure 14: the crimping of an end nipple of the toothed chain in successive process steps;

[0026] Figure 15: the pressing process with an alternative compared to Figure 14

[0027] Pressing tool; Figure 16: a toothed chain with a pressed nipple in longitudinal section;

[0028] Figure 17: the tooth link chain according to Figure 16 in perspective view;

[0029] Figure 18: an alternative toothed chain compared to Figure 17;

[0030] Figure 19: the tooth link chain according to Figure 18 in overall perspective view;

[0031] Figure 20: an alternative chain of teeth in perspective, compared to Figure 19.

[0032] The drive device 1, shown in partial detail in Figure 1, is part of a door actuation mechanism of an autonomous vehicle. The drive device 1 comprises an open toothed chain 2, a sprocket 3, and a chain support 4. The sprocket 3, which can be made of metal, plastic, or, for optimal power transmission and smooth running, rubber-coated metal, engages with the chain teeth 6 of the toothed chain 2 via its external teeth 5 to drive the chain by transmitting tensile or compressive forces in both longitudinal directions. The toothing is designed so that there is no play, or at most only very minimal play, between the tooth flanks. Pre-tensioned toothing is also possible. The chain support 4 contacts one of the chain backs 7 of the toothed chain 2, opposite the chain teeth 6, and thereby supports the drive forces of the sprocket 3 acting in the transverse direction of the chain (chain back 7 as shown in Figure 7).This prevents the chain teeth 6 from lifting off the outer teeth 5. The chain support 4 is formed in this case by support rollers 8 and 9, which roll on the chain back 7. Alternatively, a support shoe (not shown) sliding on the chain back 7 can be provided as the chain support.

[0033] When the sprocket 3 rotates clockwise, the chain section located to the right of the sprocket 3 in Figure 1 transmits compressive forces to a component of the vehicle connected to the end of this chain section. When the sprocket 3 rotates counterclockwise, this chain section transmits tensile forces to the component. This component could be the vehicle door to be operated or a body pillar, such as an A-pillar, to which the door is hinged. The transmission of tensile forces occurs via a tension member 10, symbolized by a dashed line in Figure 1, which holds the numerous chain links 11 of the toothed chain 2 together in a pivot-like contact. The chain links 11, which will be explained later, are each penetrated by one or more openings 12 in the longitudinal direction of the chain (see, for example, Figure 6) and are threaded onto the tension member(s) 10 with their openings 12.The transmission of compressive forces occurs – with negligible force transmission via the tension member 10 – essentially via the pressure contact of the chain links 11. The tension member(s) 10 can be designed as ropes, fabrics, or one or more bands made of flexible but tensile-resistant material. The chain section extending to the left of the sprocket 3 in Figure 1 has a free end and is essentially unloaded.

[0034] The chain's longitudinal and transverse directions define a plane of curvature in which the operationally loaded toothed link chain 2 bends in both directions. The chain sections extending to the left and right of the sprocket 3 are curved in one direction away from the chain teeth 6 and consequently from the sprocket 3, while the intermediate chain section, which is currently engaged with the sprocket 3, is curved in the other direction, i.e., in the same direction as the sprocket 3. As explained in more detail below, the chain links 11 are geometrically designed such that the operational curvature of the toothed link chain 2 is limited in at least one direction, and in this case in both directions, by mutual contact of the chain links 11 outside their pivot joints 13 (see Figures 2 and 3).In one direction of curvature, the operational curvature is limited to a maximum value at which the compressive forces are reliably transmitted with sufficiently high arc stability and without buckling of the toothed chain 2. In the other direction of curvature, the operational curvature – optional, but provided for here – is limited to a value only slightly greater than the curvature of the external teeth 5 of the sprocket 3. The tooth radius of the sprocket 3 is dimensioned so that the tensile cords 10 can be curved to their maximum extent with fatigue strength.

[0035] Figure 2 shows a pair of the immediately adjacent chain links 11 from Figure 1. The chain links 11 are identical parts and are made of a metallic material with a high modulus of elasticity and a high yield strength. For lower strength requirements, plastics, etc., are also conceivable. The pivot joints 13 are each formed by a convex cylindrical segment 14 and a concave cylindrical segment 15 that conforms to it, located above the chain teeth 6, which rise in the transverse direction of the chain, and below the chain back 7.The chain curvature is limited by the mutual contact of the chain links 11 outside the pivot joint 13: In the other direction of curvature, the curvature is limited by the contact surfaces 16 and 17, which are wedge-shaped apart when the toothed link chain 2 is not curved, and in one direction of curvature, by the contact surfaces 18 and 19, which are also wedge-shaped apart when the toothed link chain 2 is not curved, through partial or full contact. This limitation of curvature in the other direction of curvature ensures reliable tooth engagement in the area between the support rollers 8 and 9. The inclination of the contact surfaces 18 and 19 with respect to the transverse direction of the chain is such that, when extended imaginarily, the contact surfaces 18 and 19 intersect at the center of curvature of the chain section located to the right of the sprocket 3 in Figure 1.The mutual contacts of the contact surfaces 16, 17 and 18, 19 to the pivot joints 13 can be adjusted in direction and distance to the tension member 10 so that the friction in the pivot joint 13 and an additional force on the tension member 10 are optimized.

[0036] The chain links 11 and 11' shown in Figure 3 are different from each other. In this second variant, chain link 11 comes from a first group with identical first chain links 11, and the second chain link 11' comes from a second group with identical second chain links 11'. The chain links 11 and 11' are threaded alternately onto the tension member 10. The chain links 11 and 11' are each symmetrical to the transverse direction of the chain, with the first chain link 11 having convex cylindrical segments 14 on both sides and the second chain link 11' having concave cylindrical segments 15 on both sides.

[0037] In the third variant according to Figure 4, the chain links 11 and 11' have contact surfaces 18 and 19 which are inclined relative to the transverse direction of the chain.

[0038] In the fourth and fifth variants according to Figures 5 and 6, respectively, the contact surfaces 16, 17 and 18, 19 are each designed such that the force introduced by the chain teeth 6 does not transmit a moment to the pivot joints 13 and therefore does not cause the chain links 11 to tilt. Unlike the previously described chain links 11 with several, and in this case four, circular openings 12 for the corresponding number of tension strands 10 with circular cross-section, the chain link 11 shown in Figure 7 has only one oblong opening 12 for a tension strand 10, the cross-section of which is oval, rectangular, or also oblong.

[0039] The geometry of the chain links 11 described above is difficult to produce using forming techniques in conjunction with metallic materials. In particular, shaping the chain teeth 6 and the swivel joints 13 is challenging. Furthermore, the driving force of the sprocket 3 must be transmitted from the chain teeth 6 to the swivel joints 13, which are arranged offset from them, resulting in a bending load on the chain links 11.

[0040] It is therefore proposed to replace the difficult-to-manufacture features swivel joint 13 and chain tooth 6 with a recess for inserting a needle 20, as is common, for example, in needle bearings or roller freewheels. The needles 20 have the following advantages over being formed during the forming process:

[0041] • Low price

[0042] • High accuracy

[0043] • High hardness and wear resistance

[0044] The chain links 11 have a recess 21, as well as openings 12 for receiving the tension cords 10, and cylindrical recesses 22 on both sides, each concave cylinder segment 15 for receiving the needles 20, each convex cylinder segment 14. The recesses 22 allow the chain links 11 to pivot against each other via the needles 20. First stops 23 and second stops 24 serve to limit the pivoting movement of the chain links 11 around the needles 20. The geometry is designed to ensure bending of the toothed chain 2 in one plane and the ability to transmit power.

[0045] In order to achieve high stability but also a flexible property of the toothed link chain 2, the first stop 23 is designed such that the toothed link chain 2 has high stability in an arc shape and can be bent in the rear direction up to a definite radius, at least up to the radius of the sprocket 3, due to the mobility around the needles 20 which serve as pivot joints 13.

[0046] In the area of ​​the recess 21, the needles 20 serve to transmit power from the sprocket 3 to the chain links 11.

[0047] Stop 24 serves to limit tilting of the chain links 11 when force is applied by the needles 20 to the sprocket 3. It can also define the minimum radius of curvature 25 of the toothed chain 2 (see Figure 1) upon contact with the sprocket 3, thus ensuring reliable tooth engagement in the area between the support rollers 8, 9.

[0048] As shown in Figures 10 to 13, it is proposed below to design the contact surfaces 18, 19 between the chain links 11 and 11' such that, when the bow is opened, contact is initially established close to the respective pivot joint 13. Under bending stress on the bow, the center of pressure of this contact is then shifted further away from the pivot joint 13, and the tension member 10 is elongated. The tension member stress thus increases when the bow of the toothed chain 2 is loaded. This gives the chain bow elastic behavior and prevents sudden contact between the chain links 11 and 11'.

[0049] The contact surface 18 is convex and comprises a first, straight surface section 18a with a slight inclination and a subsequent, second surface section 18b with a greater inclination. Thus, the arc can be formed without load by the surface sections 18a being positioned close to the pivot joint 13. Under load, the chain links 11 and 11' can roll against each other, whereby the contact point shifts on the surface sections 18a and 18b and the tension member 10 is elongated. This makes the arc of the toothed chain 2 definably more elastic until the surface sections 18b are fully in contact.

[0050] In other words, it is proposed that the mutually facing contact surfaces 18, 19 in the direction of curvature away from the sprocket 3 (see Figure 1) only make point or line contact, with the distance of this point or line contact to the respective pivot joint 13 increasing with the curvature of the toothed chain 2 in this direction of curvature. The geometry is designed such that bending of the toothed chain 2 in one plane and the ability to transmit force are ensured.

[0051] In order to achieve high stability but also a flexible property of the toothed link chain 2, the contact surface 18 is designed such that the toothed link chain 2 has high stability in an arc shape and can be bent in the rear direction up to a defined radius 25 (see Figure 1), at least up to the radius of the sprocket 3, due to the mobility of the swivel joints 13.

[0052] Stop 24 serves to limit tilting of the chain links 11, 11' when the chain teeth 6 are subjected to force from the sprocket 3. It can also define the minimum radius of curvature 25 of the toothed chain 2 upon contact with the sprocket 3, thus ensuring reliable tooth engagement in the area between the support rollers 8, 9. Stop 24 can be adjusted in direction and distance to the tension member 10 to optimize friction in the pivot joint 13 and the additional force on the tension member 10.

[0053] Figures 12 and 13 show embodiments with stop 24 such that the force introduced by the chain tooth 6 does not transmit a moment to the pivot joint 13, and therefore does not cause the complete chain links 11 to tilt.

[0054] As already explained for Figures 2 and 3, the pivot joints 13 are formed by matching cylindrical segments 14, 15 of adjacent chain links 11, 11'. These can be formed either by symmetrical chain links 11, 11' with alternating convex and concave cylindrical segments 14, 15, or by a series of identical chain links 11 with a convex cylindrical segment 14 or 15 on one side and a concave cylindrical segment 15 on the other. In the latter case, all chain links 11 have the same shape. This requires directional assembly.

[0055] The toothing is designed so that there is no or only minimal play between the tooth flanks. Pre-tensioned toothing is also possible. As with link chains, the toothing in the arrangement according to the invention can also be selected such that the curvature of the toothed link chain 2 to the sprocket radius creates a pre-tension between the external teeth 5 of the sprocket 3 and the chain teeth 6 of the chain links 11, 11'. Additionally, it is proposed to design the mutual sprocket-side stops 24 between the chain links 11, 11' such that the minimum radius of curvature 25 (see Figure 1) of the toothed link chain 2 is limited and is larger than necessary to wrap around the sprocket 3. This creates a geometrically defined pre-tensioned arc in the area between the support rollers 8, 9 and the sprocket 3, and reduces a (critical) bending stress on the tension member 10.Due to the elasticity of this arc section, the risk of complete unloading of one of the two support rollers 8, 9 can be reduced, which further improves the system's feel. In contrast to the preceding explanations, the stop 24 is to be used as a limit to the minimum radius of curvature 25 in the direction of the sprocket 3.

[0056] Assembly process of the toothed chain:

[0057] Steel cable structures are typically prestressed using bolted connections at the cable ends. To generate reproducible prestressing forces, it is necessary to monitor the tightening torque, which is highly dependent on thread friction. This leads to inaccurate prestressing forces and long assembly times. Furthermore, this type of prestressing requires many individual components.

[0058] The nipple 26, which is pressed onto the end of the steel cable anyway, is designed and pressed in such a way that the pretension force is generated in the tension member 10, which is designed as a steel cable 27, during the pressing process. The volume displaced during the pressing of nipple 26 is utilized for this purpose. The forming process is designed so that pressing the nipple results in a change in length along the axis of the steel cable, which generates a defined pretension force in the steel cable 27. The pretension force can then be calculated from the pressing force and ensured during the assembly process throughout series production.

[0059] Process step 1 according to Figures 14a and 14b:

[0060] In this first step, the necessary elements 28 for the respective construction are threaded onto the steel cable 27. Finally, the nipple 26 is threaded onto the cable. Then, the nipple 26 is positioned between the press jaws 29a and 29b. Process step 2 according to Figures 14c and 14d:

[0061] The press jaws 29a and 29b close until they make contact with the nipple. The travel and pressing force are zeroed. The tool must be designed so that a change in volume is only possible in a longitudinal direction relative to the steel cable axis.

[0062] Process step 3 according to Figures 14e and 14f:

[0063] Press jaws 29a, 29b are compressed with a defined pressing force F. The tool must be designed such that a change in volume is only possible in a longitudinal direction relative to the steel cable axis. The pressing force F generated here directly influences the change in volume and also the length growth of the nipple 26, thereby generating a targeted pretension force in the steel cable 27. By monitoring the pressing force F, the steel cable pretension force can be monitored during the series production process.

[0064] Further details according to Figures 15a to 15d, which show an alternative pressing tool in different views:

[0065] 1. The outer contour of the tool closes, so that the nipple 26 is bandaged and can only flow in one direction.

[0066] 2. Now, tool slides 30 are loaded, causing the material to flow, and the pressing force F can also be output.

[0067] 3. During process development, the nipple elongation is determined as a function of the pressing force. The pressing force F is then monitored during the process.

[0068] Figure 16 shows the end of a toothed link chain 2 with a crimped nipple 26.

[0069] Figure 17 shows a toothed link chain 2 with pressed nipples 26, each having a circular cross-section.

[0070] Figure 18 shows a toothed chain 2 with pressed-on nipples 26, each having a hexagonal cross-section. Figures 19a and 19b show the toothed chain 2 according to Figure 18 in a perspective view of the entire structure. The sprocket 3 according to Figure 1 engages with the teeth 6 in the middle of the toothed chain 2, which are set back in the transverse direction of the chain, as shown in Figure 19b.

[0071] Figures 20a to 20c show a toothed link chain 2 in a perspective overall view or as an end-side section, wherein the nipples 26 have a hexagonal cross-section that is flattened compared to Figure 18.

Claims

Patent claims 1. Toothed link chain (2) with mutually pivotally contacting chain links (11, 11'), each forming a chain tooth (6) rising in the transverse direction of the chain, characterized in that the toothed link chain (2) transmits both tensile and compressive forces in its longitudinal direction and the chain links (11, 11') are penetrated in the longitudinal direction of the chain by an opening (12), wherein the toothed link chain (2) has a tensile member (10) on which the chain links (11, 11') with their openings (12) are threaded, the longitudinal and transverse directions of the chain define a plane of curvature in which the toothed link chain (2) bends operationally in both directions of curvature, and the operational curvature of the toothed link chain (2) in the direction of curvature facing away from the chain teeth (6) is determined by mutual contact of the chain links. (11, 11') is restricted outside their pivot joints (13).

2. Toothed link chain (2) according to claim 1, characterized in that the chain links (11, 11') contact each other over a surface in one direction of curvature.

3. Toothed link chain (2) according to claim 1, characterized in that the chain links (11, 11') contact each other only in a point or line-like manner in one direction of curvature, wherein the contact distance to the respective pivot joint (13) increases with the curvature of the toothed link chain (2) in this direction of curvature.

4. Toothed link chain (2) according to claim 3, characterized in that one of the mutually facing contact surfaces (18, 19) is convex and comprises a first, straight surface section (18a) with a slight inclination and a second surface section (18b) adjoining it with a greater inclination.

5. Toothed link chain (2) according to one of the preceding claims, characterized in that the pivot joints (13) are each formed by a convex cylindrical segment (14) and a concave cylindrical segment (15) that fits snugly against it.

6. Toothed link chain (2) according to claim 5, characterized in that the convex cylindrical segment (14) is formed by a needle (20) which is in a recess (22) is recorded as a concave cylindrical segment (15).

7. Toothed link chain (2) according to claim 5, characterized in that either the chain links (11) are identical parts or that the chain links (11, 11') comprise a first group with identical first chain links (11) and a second group with identical second chain links (11'), wherein the first chain links (11) each have the convex cylindrical segments (14) on both sides and the second chain links (11') each have the concave cylindrical segments (15) on both sides.

8. Toothed link chain (2) according to one of the preceding claims, characterized in that the tension member (10) has a circular, oval or rectangular cross-section.

9. Drive device (1) comprising a toothed link chain (2) according to one of the preceding claims, a sprocket (3) which drives the toothed link chain (2) with an external toothing (5) engaging with the chain teeth (6) in both chain longitudinal directions, and a chain support (4) which contacts a chain back (7) of the toothed link chain (2) facing away from the chain teeth (6) and supports the drive forces of the sprocket (3) acting in the chain transverse direction, wherein the chain support (4) either rolls or slides on the chain back (7).

10. Drive device (1) according to claim 9, characterized in that the chain links (11, 11') have mutual stops (24) which limit the operational curvature of the toothed link chain (2) in the direction of curvature of the sprocket (3), wherein the minimum radius of curvature (25) is larger than is necessary to wrap around the sprocket (3).

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