LINEAR DRIVE, LENGTH ADJUSTMENT UNIT WITH SUCH A LINEAR DRIVE

Description

[0001] The present invention relates to a linear drive with the features of claim 1, a longitudinal adjustment unit for a seat with the features of claim 14 and a motor vehicle with the features of claim 15.

[0002] Linear actuators are known in various configurations from the prior art and are widely used as longitudinal adjustment units for adjusting the position of a seat in motor vehicles. Longitudinal adjustment units typically interact with a lower rail fixed to a chassis and an upper rail arranged within it, the upper rail being movable by the longitudinal adjustment unit and coupled to the seat. In the prior art, the adjustment of the upper rail by the longitudinal adjustment unit is typically achieved by means of a spindle arranged within the upper rail and supported at its respective first and second ends. Such longitudinal adjustment units are known, for example, from DE 36 40 197 A1, DE 42 08 948 C2, DE 196 42 655 C2, DE 198 15 283 A1, DE 10 2004 013 009 A1, JP 2022 143776 A, WO 2020 245 255 A1, JP H06 84054 U and DE 10 2006 052 936 A1.Due to the high demands placed on a linear drive, which in addition to its adjustment function as a longitudinal adjustment unit must also guarantee accident safety, such linear drives have different designs that require different manufacturing methods and processes.

[0003] On the downside, it has been shown that achieving backlash-free linear motion is only possible with considerable effort, and that adjusting the breaking loads of such linear drives is also extremely difficult. Furthermore, existing longitudinal adjustment units are only suitable to a limited extent for implementing novel seating concepts in vehicles. It has also been observed that the backlash-free operation of the linear drives is lost due to wear.

[0004] This is where the present invention comes in.

[0005] The invention is based on the objective of proposing an improved linear drive that advantageously eliminates the disadvantages known from the prior art. Furthermore, a linear drive with a particularly compact design is preferred, which in particular enables smooth and virtually backlash-free linear movement with a simultaneously variable and adjustable breaking load. In addition, the proposed linear drive should be capable of achieving a high adjustment speed and exhibit improved wear characteristics.

[0006] These tasks are solved by a linear drive with the features of claim 1, a longitudinal adjustment unit with the features of claim 14 and a motor vehicle with the features of claim 15.

[0007] The linear drive according to the invention comprises at least one rack oriented along a longitudinal axis, at least two slides movable transversely to the longitudinal axis, and a drive shaft. The at least two slides are coupled to the drive shaft such that each slide performs at least one cyclic movement, offset from each other in phase, during one revolution of the drive shaft. During this movement, the slides, through operative contact with the at least one rack, are pushed along the rack to generate a thrust in a direction along the longitudinal axis. Furthermore, the invention provides that the linear drive includes at least one compensating means by which the operative contact between at least one of the at least two slides and the at least one rack is spring-loaded or pre-tensioned.

[0008] The present invention is based on the idea of ​​proposing a linear drive comprising at least one compensating means by which tolerances and / or wear can be compensated. The at least one compensating means is designed such that the operative contact between at least one of the at least two slides and the at least one rack is spring-loaded, in particular pre-tensioned. In the event of tolerances and / or wear, the at least one compensating means enables the at least one rack and / or at least one of the at least two slides to perform a compensating movement. The compensating means thus creates an approximately backlash-free linear drive, which is preferably also particularly smooth-running and quiet, and furthermore preferably has a long service life.

[0009] A further development of the present invention provides that the at least one compensating means provides spring action, in particular preload, to at least one of the at least two slides and / or the at least one rack in a transverse axis oriented substantially transversely to the longitudinal axis. For example, by preloading the at least one rack transversely to the longitudinal axis, the at least one rack can undergo a displacement, preferably limited on at least one side by stops, by which any play due to tolerances and / or wear can be compensated. In other words, the at least one rack can perform the compensating movement opposite to the cyclic movement of the at least one of the at least two slides.

[0010] According to the present invention, at least two racks are provided. The at least two racks can, for example, each be arranged on its own rail or on a common rail.

[0011] Furthermore, the at least two racks are arranged opposite each other in such a way that a cam is formed between them. At least one of the at least two sliders can engage in this cam and, during the cyclical movement, alternately slide against the two opposing racks. The cam can thus be designed as a wave-shaped or zigzag-shaped groove along the longitudinal axis and comprises two opposing profile surfaces, which are provided by the two opposing racks.

[0012] The two opposing profile surfaces can have any number of teeth, each formed from a rising and a falling tooth flank, the point or section between two adjacent tooth flanks being referred to here as a transition. Preferably, the transitions of two opposing profile surfaces of a cam are arranged approximately transversely to the longitudinal axis in a straight line.

[0013] According to a preferred embodiment, at least one of the at least two racks is preloaded against the other, opposite rack by the at least one compensating means. Preferably, only one of the two opposite racks is fixed relative to the other, while the other rack can perform a compensating movement via the at least one compensating means. The at least one of the at least two sliders that engages in the cam is fixed between the two racks, and any play, for example due to tolerances or wear, can be compensated for.

[0014] A further development of the present invention provides that the at least one slide comprises at least one pin. Preferably, the at least one slide is in operative contact with the at least one rack via the at least one pin. The at least one pin can preferably be integrally formed with a slide body or be attached to the slide body. For example, the at least one pin can be inserted or pressed into a receptacle of the slide body.

[0015] The at least one pin can, for example, be designed like a tooth, the shape of which corresponds to the profile of the at least one rack. Such a tooth is advantageous, for example, for forming a surface contact between the at least one slide and the at least one rack. Alternatively, the pin can also have a round, polygonal, or similar cross-section.

[0016] A further development of the present invention provides that the at least one pin projects into the guide track in each pin axis and is fixed in the track between the two opposing racks, preferably in the longitudinal axis. For this purpose, the respective pin axis is preferably oriented in the direction of a normal vector of a rail plane, which is spanned by the longitudinal axis and the direction of the cyclic movement.

[0017] A preferred embodiment of the present invention provides that the at least one pin is pre-tensioned in a plane transverse to the cyclic movement of at least one of the at least two slides by means of the at least one compensating means, and / or that the at least one pin is pre-tensioned in the pin axis by the at least one compensating means. The compensating means pre-tensions the operative contact between the slide and the respective rack.

[0018] According to the present invention, the cam has two opposing and converging profile surfaces. In other words, the groove-shaped cam does not have a constant width, but rather its width increases and / or decreases in the orientation of the pin axis.

[0019] Furthermore, it has proven advantageous if the at least one pin has a shape corresponding to the tapered profile surfaces. For example, the at least one pin can be at least partially pyramidal and / or conical, whereby the at least one pin is in operative contact with the respective rack along the pin axis, the operative contact preferably being a line contact or, even more preferably, a surface contact.

[0020] By pre-tensioning the at least one pin using the at least one compensating element, the operative contact between the at least one pin and the at least one tooth profile is pre-tensioned. This pre-tensioning causes the respective at least one pin to be displaced along its axis by the compensating element, for example, in the event of wear, thereby compensating for wear and / or possibly also tolerances. According to a further embodiment of the present invention, the at least one pin is formed from at least two individual pins arranged in a common plane perpendicular to the longitudinal axis. Two individual pins are also referred to as a single-pin pair in connection with this invention. The at least two individual pins preferably alternately make operative contact with the respective rack during a cyclic movement.According to a preferred embodiment, the individual pins have a common and, even more preferably, integrally formed base, wherein the base can, for example, also be formed by the slide body. The two individual pins have a lower stiffness than a single pin and can, in particular, compensate for tolerances and / or wear caused by deformation, especially elastic deformation, through elastic deformation.

[0021] A preferred embodiment of the present invention provides that at least one compensating means is arranged between at least two single pins or a pair of single pins, which preloads the at least two single pins.

[0022] A further embodiment of the present invention provides that the at least one pin comprises a sheath and a pin body. According to an advantageous embodiment of the present invention, at least one compensation means is arranged between the sheath and the pin body. Preferably, several compensation means, preferably circumferentially symmetrical, are arranged between the sheath and the pin body, the compensation means allowing elastic displacement of the sheath relative to the pin body. This makes it possible, for example, to compensate for tolerances and / or wear.

[0023] A further development of the present invention provides that the sheath is held rotationally fixed to the pin body, which is preferably cylindrical. Preferably, the sheath is rhombus-shaped, and the compensating means are arranged either in the corner regions of the rhombus or, more preferably, on the side edges. To prevent the sheath from twisting relative to the pin body, the pin body can have at least one projecting rib that serves for a positive-locking transmission of torques between the pin body and the compensating means. The sheath can thus perform not only a compensating movement in a plane perpendicular to the pin axis, but also a torsional movement.

[0024] Furthermore, it has proven advantageous to arrange several racks in series along the longitudinal axis, thereby extending the travel path along the longitudinal axis for the linear drive as desired. Preferably, the racks arranged in series along the longitudinal axis can be positively connected to one another. For example, the racks arranged in series along the longitudinal axis can be positively connected in the manner of a dovetail joint. Alternatively, a coupling element can be provided that connects two adjacent racks along the longitudinal axis. For example, the coupling element can be formed by a compensating element, which can be made, for example, of an elastic polymer, rubber, or a soft, elastic metal.To compensate for any tolerances and / or wear, at least one rack can be slightly movable in the longitudinal axis.

[0025] A further development of the present invention provides that the operative contact between the at least one rack and at least one of the at least two slides is a surface contact, a line contact, or a radio contact. Surface contact is achieved, for example, by the slide having running surfaces that correspond at least partially to the rack and interact with the respective rack or profile surface. Line contact is achieved, for example, by a cylindrical section on the slide, in particular the pin, and radio contact can be achieved, for example, by a correspondingly curved design of either the at least one rack and / or the slide, in particular the pin.

[0026] A further development of the present invention provides that the at least one compensation means comprises an outer layer arranged on the at least one rack and / or on the at least one slide. The outer layer can be made of a softer material, and for backlash compensation, the tooth flanks of the respective rack are preferably coated with the outer layer. This also allows manufacturing or assembly tolerances between the individual contact surfaces of the slides and the racks to be compensated. Furthermore, it can be advantageous if the outer layer has improved sliding properties, which on the one hand reduces the sliding friction between the slide and the respective rack and on the other hand positively influences noise generation. For example, the outer layer can be made of PTFE.

[0027] It is also conceivable to form at least one surface layer on the slide. In particular, it is preferred if the pin is coated with the surface layer. Furthermore, it can be advantageous if at least one of the at least two slides also has a surface layer in the area where the mechanical coupling between the drive shaft and the respective slide takes place. The surface layer also allows for a backlash-free coupling between the respective slide or the drive shaft, and tolerances and / or wear can be compensated for there as well.

[0028] Furthermore, the present invention relates to a longitudinal adjustment unit with a linear drive according to the invention.

[0029] Another aspect of the present invention relates to a motor vehicle with at least one such linear drive according to the invention.

[0030] An exemplary embodiment of the invention and further developments of the present invention are described in detail below with reference to the accompanying drawings. The drawings show: Figure 1 shows a perspective view of a linear drive with a drive shaft driven by a drive unit, four racks and two slides coupled to the drive shaft in such a way that they each perform a cyclic and mutually phase-shifted movement during one revolution of the drive shaft and thereby slide against at least one rack to generate a thrust in one direction of the longitudinal axis. Figure 2 shows a sectional view of the Figure 1 Figure 3 shows another sectional view of the Figure 1Figure 4 shows a highly simplified, enlarged, and schematic representation of the linear drive 1 according to a first embodiment, wherein one of the two opposing racks is spring-loaded and pre-tensioned transversely to the longitudinal axis by a compensating means; Figure 5 shows a second embodiment, wherein a surface layer is provided on the tooth flanks of the racks; Figure 6 shows a third embodiment and a detailed view of a pin of a slide, wherein at least one pin comprises a pin body and a sheath, and wherein the sheath is pre-tensioned by the compensating means; Figure 7 shows a fourth embodiment by analogy to Figure 6 Figure 8, 6, a fifth embodiment analogous to Figure 9, a sixth embodiment analogous to Figure 6, Figure 10, a seventh embodiment analogous to Figure 6Figure 11 shows a highly simplified detail of an eighth embodiment of the linear drive, wherein two opposing racks form a cam whose profile surfaces are converging, and wherein the pin is conical. Figure 12 shows a ninth embodiment by analogy to Figure 11 Figure 13 shows a tenth embodiment, wherein the slide has two pins, and wherein each pin is formed from two individual pins which are pre-tensioned by the compensating means, and Figure 14 shows an eleventh embodiment, wherein the compensating means connects two racks arranged in series along the longitudinal axis, and Figure 15 shows a detailed view of the compensating means according to Figure 14 .

[0031] Identical or functionally equivalent parts or features are identified by the same reference numerals in the detailed description of the figures below. Furthermore, not all identical or functionally equivalent parts or features in the figures are assigned a reference number.

[0032] Figure 1 Figure 1 shows an exemplary simplified and perspectively depicted embodiment of a linear drive 1, which can be used, for example, in a longitudinal adjustment unit 2 for a (not shown) seat of a (not shown) motor vehicle.

[0033] The linear drive 1 according to Figure 1 comprises a rail 10 oriented along a longitudinal axis L, at least two sliders 30 which - as in Fig. 2 shown - are movable transversely to the longitudinal axis L. Furthermore, the linear drive 1 comprises at least one driveable drive shaft 60, which is rotatable in a rotary axis X.

[0034] The at least one rail 10 is oriented along the longitudinal axis L, where, for example, the longitudinal axis L can be defined by a vehicle longitudinal axis of the motor vehicle. The rail 10 has at least two racks 20, and it should be noted that in the illustrated embodiment, the linear drive 1 comprises two rails 10, each with two racks 20.

[0035] According to the Figures 1 to 3 Two racks 20 are arranged opposite each other on a rail 10 such that a cam 24 is formed between the at least two racks 20, into which at least one of the at least two slides 30 engages and, during the cyclic movement, can alternately slide along the two opposing racks 20. The cam 24 can be designed in the form of a groove and comprises two opposing profile surfaces 25, 26, which are formed by the two opposing racks 20.

[0036] The two racks 20 preferably span a rail plane E which is oriented parallel to the longitudinal axis L.

[0037] The cam 24, designed as a groove or opening, extends in the direction of the normal vector into the rail 10.

[0038] Scenery 24 preferably has a constant scene depth.

[0039] Scene 24 according to the detailed illustration in Figure 3 comprises the two opposing profile surfaces 25, 26, which extend in a zigzag or wave shape at a permanent distance A1 to form a tooth profile 21 with a plurality of teeth 22.

[0040] The teeth 22 have symmetrical flanks 25a, 25b, 26a, 26b that extend on both sides between the tooth tip and the tooth base. Two adjacent tooth tips are arranged at a tooth spacing A2, or the length of a tooth 22 along its longitudinal axis corresponds to the tooth spacing A2.

[0041] The tooth profile 21 can, among other things, Figures 1 and 2 can be removed, extending completely along the longitudinal axis L over the rail 10.

[0042] The embodiment shown in the accompanying figures depicts at least two slides 30, it being noted here that a single slide 30 is sufficient to generate a thrust in a direction L1 or L2 of the longitudinal axis L.

[0043] The two sliders 30 of a linear drive 1 can be, as in the embodiment according to the Figures 1-3 The components shown are essentially identical in construction and can either be arranged on opposite sides of the drive unit along the longitudinal axis or, in an embodiment not shown, on a single side of the drive unit.

[0044] The respective slide 30 is coupled to the driven drive shaft 60 in such a way that the respective slide 30 performs at least one cyclic movement during one revolution of the drive shaft 60.

[0045] The slide 30 can have an opening or recess in the formed contact area 34. The contact area 34 preferably extends along the axis of rotation X and can have a width B2 and a height H2.

[0046] To generate the thrust in one direction of the longitudinal axis L, the slide 30 engages in the cam 24 of the rail 10. For this purpose, the slide 30 can include a running surface 45 which is designed to be in operative contact with the opposing profile surfaces 25, 26.

[0047] As in Figure 3As can be seen, the running surface 45 can be formed on a pin 40 which engages in the cam 24 in a pin axis P from a base body 31 of the slider 30 transversely to the longitudinal axis L and perpendicular to the rail plane E.

[0048] Each slider 30 can have several pins 40, wherein a distance A3 between two pins 40 in the longitudinal axis of a slider 30 corresponds to the distance A1.

[0049] Pin 40 can be cuboid, rhombus-shaped (see Figures 3 to 7 ) or a round one (see Figure 9 and 10 ) have a cross-section and can be integrally formed with the base body 31 or attached to the base body 31 of the slide 30, in particular inserted or pressed in.

[0050] How Figure 3As can be seen, pin 40 has a width B1, measured perpendicular to the longitudinal axis L. Preferably, the width B1 corresponds approximately to the distance A1 between the two profile surfaces 25, 26, i.e., B1 ≈ A1.

[0051] The running surface 45 can have a surface with improved friction properties to reduce the friction between the cam 24 and the slider 30.

[0052] The slide 30, in particular the at least one pin 40 of the slide 30, is preferably positively locked in the longitudinal axis L between two opposing profile surfaces 25, 26. The positive locking in the longitudinal axis L between the slide 30 and the cam 24 can block unwanted movement or free play of the linear drive 1.

[0053] The coupling between the drive shaft 60 and the respective slide 30 can be effected in different ways, whereby, according to the embodiments presented here, the coupling can be effected by means of guide means 62, which interact with the slide 30, in particular with the contact area 34. The slide 30 can have at least one contact surface 36 in the contact area 34, which interacts with the guide means 62.

[0054] The guidance tool 62 can, for example, be used as described in the accompanying documentation. Figures 1-3 is shown to be designed as a camshaft disc 63 of a crankshaft or camshaft, and engage in the opening or recess of the slide 30 and interact there with the contact area 34.

[0055] The drive shaft 60 can be driven by a drive device 70, wherein the drive device 70 is preferably an electric drive which is further preferably coupled to the drive shaft 60 via a (not shown) gearbox.

[0056] The guide element 62 or the camshaft disc 63 can be described as being essentially heart-shaped.

[0057] The guide element 62, or camshaft disc 63, has a running surface 64 which is formed at a distance in the direction of rotation from an axis of rotation X of the drive shaft 60. The distance between the running surface 64 and the axis of rotation X changes in the direction of rotation such that the distance increases predominantly linearly in one direction of rotation in at least a first half and decreases linearly in the direction of rotation in at least a second half. The running surface 64 has an approximately spiral profile in each half, and is preferably designed such that the distance between two diametrically opposed sides, measured across the axis of rotation X, is approximately constant.

[0058] By means of the drive coupling of the at least one slide 30 with the drive shaft 60, the respective slide 30 is set into at least a linear and cyclical motion transverse to the longitudinal axis during one revolution of the drive shaft 60, wherein the cyclical motion of the respective slide 30 takes place in the plane of the rail E or parallel to the plane of the rail E. The double arrow in Figure 3 This is intended to illustrate the cyclical movement in the rail plane E or parallel to the rail plane E of the slide 30.

[0059] During the cyclical movement of the at least one slide 30, the slide 30 alternately slides against the opposite profile surfaces 25, 26 in the longitudinal axis L to generate the thrust. In other words, the slide 30 moves about the axis of rotation X transversely to the longitudinal axis L for at least one revolution of the drive shaft 60.

[0060] A complete cycle of movement, starting from an initial position, comprises movement in a first direction Y1 and a change of movement to a second direction Y2 at a turning point. The movement in the second direction Y2 continues until the next turning point. Finally, the movement returns to the initial position.

[0061] Figure 4 Figure 1 shows a schematic representation of an exemplary designed linear drive 1 with a compensation means 15, by which play and / or wear can be compensated.

[0062] In the illustrated embodiment, the compensating element 15 can be formed by elastic spring elements (not shown in detail) by which one of the two racks 20 is biased against the other, opposite rack 20. The compensating element 15 is illustrated by arrows.

[0063] For better understanding, the racks are shown in Figure 4 characterized by the reference numerals 20 and 20', wherein the rack 20 is fixedly arranged, for example fixedly on the (not shown) rail 10, and the other rack 20' is biased transversely to the longitudinal axis L by the compensating means 15 against the rack 20.

[0064] By preloading the rack 20' to the fixed rack 20, the pin 40 is fixed in the cam 24 and the play and / or wear can be compensated.

[0065] End stops (not shown) can be provided for the rack 20', which limit the maximum displacement of the rack 20' transverse to the longitudinal axis L by the compensating means 15. The end stops are intended to prevent the profile overlap between the two racks 20, 20' from becoming too small.

[0066] A second embodiment of a linear drive 1 with a compensation means 15 can Figure 5 The at least one compensation means 15 can comprise an outer layer 16, which is arranged on the at least one rack 20 and / or on the at least one slide 30, in particular on its running surface(s) 45. The outer layer 16 can be made of a softer material, wherein, for backlash compensation, the profile surfaces 25, 26 of the respective rack 20 are preferably coated with the outer layer 16. In addition, it can be advantageous if the outer layer 16 has improved sliding properties, which can further reduce the sliding friction and / or the noise generation between the slide 30 or its pins 40 and the respective rack 20. As in Figure 5The compensating means 15 of the individual embodiments can be combined. For example, a surface layer 16 and a preload of one of the racks 20' transverse to the longitudinal axis L can be provided. These embodiments can also be combined arbitrarily with the embodiments described below.

[0067] According to an embodiment of the linear drive 1 (not shown), a surface layer 16 can be arranged on the guide means 62 or the camshaft disk 63 and / or on the contact area 34 of the slide 30. This allows the mechanical coupling between the drive shaft 60 and the respective slide 30 to be designed to be approximately backlash-free, and tolerances and / or wear between the guide means 62 and the slide 30 can also be compensated for.

[0068] Figure 6Figure 1 shows a compensation means 15 according to a third embodiment, wherein the compensation means 15 is arranged on the pin 40 of the at least one slider 30.

[0069] The enlarged detail view of pin 40 according to the Figures 6a and 6b It can be deduced that each pin 40 comprises a pin body 41 and a sheath 42. Furthermore, individual segments 43 may be provided by which the sheath 42 can be supported and held against the pin body 41. The sheath 42 has the running surfaces 45.

[0070] The pin body 41 can be an essentially cylindrical body, as shown. The sheath 42 can be a diamond-shaped sleeve, see Figures 6-9 be, inside which the pin body 41 can be arranged. Alternatively, the casing 42 can also have a round, in particular cylindrical or conical, outer geometry according to Figure 10 exhibit.

[0071] The compensating device 15 can create a preload - indicated by the arrows in Figure 6b - generate forces by which the individual segments 43 are pressed against the casing 42. For example, the compensating means 15 can be designed in the manner of a spring-loaded expansion anchor.

[0072] The sheathing 42 can thus undergo an elastic displacement relative to the pin body 41, which can compensate for wear and / or tolerances, for example.

[0073] The individual segments 43 can be symmetrically distributed over the circumference of the pin body 41, wherein preferably at least two, preferably three and even more preferably four individual segments 43 are provided.

[0074] The individual segments 43 can form the compensating means 15 and, for example, brace the sheathing 42 against the pin body 41.

[0075] The Figures 7a and 7bshow a fourth embodiment, wherein, in contrast to the one in the Figures 6a and 6b In the depicted pin 40, the individual segments 43 are not arranged in the corners of the diamond-shaped casing 42, but rather between the sides of the diamond-shaped casing 42 and the pin body 41. Thus, the individual segments 43 are located in the direct force path between the running surfaces 45 of the pin 40 and the pin body 41.

[0076] The Figures 8a and 8b Figure 5 shows a fifth embodiment, wherein a single segment 43 is provided between the sheath 42 and the pin body 41. The pin body 41 and / or the sheath 42 can be made of a durable or solid material, such as metal, and the segment 43 can, for example, be formed from an elastic intermediate mass as a compensating element 15, by which the sheath 42 can be spring-loaded and / or spring-loaded and pre-tensioned relative to the pin body 41.

[0077] As in the Figures 9a and 9b As shown, an anti-rotation device can be provided between the pin body 41 and the sheath 42, thereby radially stabilizing the sheath 42 and preventing it from rotating relative to the pin body 41. For example, the anti-rotation device can be formed by at least one rib 46 projecting from the pin body 41 and / or the sheath 42, through which a torque-transmitting connection can be formed between the at least one individual segment 43. The anti-rotation device can form a torsional spring mechanism, allowing for spring-loaded rotation between the pin body 41 and the sheath 42 to compensate for tolerances and / or play. The anti-rotation device also prevents the connection between the pin body 41 and the individual segment 43 and / or between the sheath 42 and the individual segment 43 from loosening.

[0078] Figures 10a and 10bshow a further embodiment. This embodiment is analogous to the embodiment described above. Figure 9 formed, however the casing 42 is not diamond-shaped but cylindrical.

[0079] Exemplary embodiments of the invention are described in the Figure 11 and 12 depicted, whereby the in the Figure 11 and 12 The illustrated embodiments have in common that the profile surfaces 25, 26 forming the cam 24 are not arranged parallel to each other. The cam 24 has converging profile surfaces 25, 26, which causes the cam to taper or widen along the pin axis P.

[0080] The respective pin 40 can, as in the Figures 11b or 12b shown is a conical profile corresponding to the converging profile surfaces 25, 26 (see Figure 11b ) or pyramid-shaped form (see Figure 12b exhibit.

[0081] The compensation means 15 can push the respective pin 40 in the pin axis P into the cam 24, thereby enabling tolerance compensation.

[0082] It should be noted here that the shape of the pin 40 does not necessarily have to correspond to the shape of the profile surfaces 25, 26. The illustrated embodiments merely show an exemplary configuration, in which the operative contact between the respective pin 40 and the rack 20 for generating the thrust is achieved by surface contact or line contact. However, the operative contact can also be achieved by point contact, for example, if the respective pin 40 has a convex shape. Such point or line contact can also be achieved by a combination of converging profile surfaces 25, 26 with non-converging running surfaces of the respective slide 30 and vice versa.

[0083] Figure 13Figure 1 shows an enlarged view of a slider 30, according to a further embodiment. Each pin 40 comprises two individual pins 47, which are biased against each other by the compensating means 15. As the Figure 12 A compensating means 15 designed as an intermediate mass 17 can be arranged between the two individual pins 47, thereby achieving the preload of the individual pins 47 against each other.

[0084] The preload can also be provided by a compensating element 15, which is formed by an excess in the distance between the two individual pins 47 of the contour of the cam 24. This ensures that one individual pin 47 is always under tension and is pressed inwards within its elastic deformation.

[0085] A final embodiment is described in the Figures 14 and 15The linear drive 1 is shown having several racks 20 or rails 10, 10' arranged in a row. This allows the length of the linear drive 1 to be extended as desired.

[0086] Two adjacent rails 10, 10' or racks 20 along the longitudinal axis L can be connected by a dovetail joint. For example, a dovetail joint can be used for this purpose. Figure 15 The T-nut 11 shown can be used, which can form the compensating means 15. The compensating means allows at least one of the racks 20 arranged in series along the longitudinal axis L to be displaced along the longitudinal axis. This allows one of the racks 20 to perform a compensating movement relative to the adjacent rack 20 along the longitudinal axis to compensate for tolerances and / or wear. Reference symbol list

[0087] 1 Linear drive 2 Longitudinal adjustment unit 10 Rail 15 Compensation means 16 Edge layer 17 Intermediate mass 20 Rack 21 Tooth profile 22 Tooth 24 Cam 25 Profile surface 26 Profile surface 30 Slider 31 Base body 34 Contact area 36 Contact surface 40 Pin 41 Pin body 42 Sheathing 43 Single segment 45 Running surface 46 Rib 47 Single pin 60 Drive shaft 62 Guide means 63 Camshaft disc 64 Running surface 70 Drive device A1 Spacing of 25 and 26 A2 Tooth spacing A3 Pin spacing B1 Width of 40 L Longitudinal axis P Pin axis

Claims

1. Linear drive (1), comprising - at least one rack (20) oriented along a longitudinal axis (L), and - at least two sliders (30) which are movable transversely to the longitudinal axis (L), and - a drive shaft (60), - wherein the at least two sliders (30) are coupled to the drive shaft (60) in such a manner that the at least two sliders (30) each perform at least one cyclic movement that is phase-shifted relative to one another over the course of one revolution of the drive shaft (60) and, in doing so, slide off the at least one rack (20) by means of an operative contact in order to generate a propulsive movement in a direction of the longitudinal axis (L), and wherein the linear drive (1) comprises at least one compensation means (15) by which the operative contact between at least one of the at least two sliders (30) and the at least one rack (20) is preloaded, characterized in that - at least two racks (20) are provided, and that the at least two racks (20) are arranged opposite one another in such a manner that a guide slot (24) is formed between the at least two racks (20), into which at least one of the at least two sliders (30) engages and, over the course of the cyclic movement, can alternately slide off the at least two racks (20), and - the guide slot (24) comprises two opposite and converging profile surfaces (25, 26).

2. Linear drive (1) according to claim 1, characterized in that the at least one compensation means (15) preloads at least one of the at least two sliders (30) and / or the at least one rack (20) substantially transversely to the longitudinal axis.

3. Linear drive (1) according to claim 1 or 2, characterized in that one of the at least two racks (20) is resiliently preloaded against the oppositely arranged other of the at least two racks (20) by the at least one compensation means (15).

4. Linear drive (1) according to one of the preceding claims, characterized in that the at least one slider (30) comprises at least one pin (40), and that the at least one slider (30) is in operative contact with the at least one rack (20) via the at least one pin (40).

5. Linear drive (1) according to claim 4, characterized in that the at least one pin (40) projects into the guide slot (24) in each case along a pin axis (P).

6. Linear drive (1) according to claim 4 or 5, characterized in that the at least one pin (40) is preloaded by means of the at least one compensation means (15) in a plane transversely to the cyclic movement of the at least one of the at least two sliders (30) and / or that the at least one pin (40) is preloaded by the at least one compensation means (15) along the pin axis (P).

7. Linear drive (1) according to one of claims 4 to 6, characterized in that the at least one pin (40) has a shape corresponding to the converging profile surfaces (25, 26).

8. Linear drive (1) according to one of claims 4 to 7, characterized in that the at least one pin (40) is at least partially pyramidal or conical in shape.

9. Linear drive (1) according to one of claims 4 to 8, characterized in that the at least one pin (40) is formed from at least two individual pins (47).

10. Linear drive (1) according to claim 9, characterized in that the at least one compensation means (15) is arranged between the individual pins (47) and preloads the at least two individual pins (47).

11. Linear drive (1) according to one of the preceding claims, characterized in that the at least one compensation means (15) preloads the at least one of the at least two sliders (30) and / or the at least one rack (20) in the orientation of the longitudinal axis (L).

12. Linear drive (1) according to one of the preceding claims, characterized in that the operative contact between the at least one rack (20) and at least one of the at least two sliders (30) is a surface contact, a line contact, or a point contact.

13. Linear drive according to one of the preceding claims, characterized in that the at least one compensation means (15) comprises a surface layer (16) which is arranged on the at least one rack (20) and / or on the at least one slider (30).

14. Longitudinal adjustment unit (2) comprising a linear drive according to one of the preceding claims.

15. Motor vehicle comprising a linear drive (1) according to one of claims 1 to 13.