LINEAR DRIVE, LONGITUDINAL ADJUSTMENT DEVICE OF A SEAT, AND MO-TOR VEHICLE

Abstract

A linear drive has at least one rack which is arranged along a longitudinal axis and has a plurality of teeth, a drive shaft arranged in a transverse axis transversely to the longitudinal axis, and at least two propulsion elements, each having at least one propulsion tooth. The at least two propulsion elements are linearly movable in a stroke axis which is oriented transversely to the longitudinal axis and transversely to the drive shaft. The at least two propulsion elements are drivingly coupled to the drive shaft in such a manner that the at least two propulsion elements perform at least one cyclical stroke movement in the course of one rotation of the drive shaft and enter and exit the at least one rack to generate a propulsion in the longitudinal axis. The at least two propulsion elements enter and exit the at least one rack with a phase shift.

Claims

1. A linear drive (1), comprising at least one rack (10) which is arranged along a longitudinal axis (X) and has a plurality of teeth (15), a drive shaft (20) arranged in a transverse axis (Y) transversely to the longitudinal axis (X), and at least two propulsion elements (30), each having at least one propulsion tooth (35), wherein the at least two propulsion elements (30) are linearly movable in a stroke axis (Z) which is oriented transversely to the longitudinal axis (X) and transversely to the drive shaft (20), wherein the at least two propulsion elements (30) are drivingly coupled to the drive shaft (20) in such a manner that the at least two propulsion elements (30) perform at least one cyclical stroke movement in the course of one rotation (φ) of the drive shaft (20) and enter and exit the at least one rack (10) to generate a propulsion in the longitudinal axis (X), and wherein the at least two propulsion elements (30) enter and exit the at least one rack (10) with a phase shift (Δφ).

2. The linear drive (1) according to claim 1, characterized in that the following applies to the phase shift (Δφ) of the cyclical stroke movement of the at least two propulsion elements (30) in relation to a rotation (φ) of the drive shaft (20): 1/16 φ≤Δφ≤½.

3. The linear drive (1) according to claim 1, characterized in that the at least one propulsion tooth (35) of one of the at least two propulsion elements (30) is arranged with an offset (ΔX) relative to the at least one propulsion tooth (35) of the other of the at least two propulsion elements (30) in relation to the drive shaft (20) in the longitudinal axis (X) and/or in that the at least one tooth (15) of the at least one rack (10) can enter and exit one of the at least two propulsion elements (30) and is arranged with an offset (ΔX) in the longitudinal axis (X) relative to the at least one tooth (15) of the at least one rack (10), which the other of the at least two propulsion elements (30) enter and exit.

4. The linear drive (1) according to claim 1, characterized in that the at least one rack (10) and the at least two propulsion elements (30) have helical gearing at a helix angle (α).

5. The linear drive (1) according to claim 1, characterized in that a rack (10) is provided for each of the at least two propulsion elements (30), the teeth (15) of each rack (10) having in the longitudinal axis (X) an offset (ΔX) that corresponds to the phase shift (Δφ).

6. The linear drive (1) according to claim 1, characterized in that the at least two propulsion elements (30) have more than one propulsion tooth (35).

7. The linear drive (1) according to claim 1, characterized in that the at least two propulsion elements (30) are identical.

8. The linear drive (1) according to claim 1, characterized in that the at least two propulsion elements (30) are arranged in parallel and adjacent to one another transversely to the longitudinal axis (X).

9. The linear drive (1) according to claim 1, characterized in that the at least two propulsion elements (30) each have a recess (40) and in that the drive shaft (20) is drivingly coupled to the relevant propulsion element (30) in the recess (40).

10. The linear drive (1) according to claim 1, characterized in that the drive shaft (20) comprises a camshaft (22) and in that the drive shaft (20) is drivingly coupled to the at least two propulsion elements (30) via the camshaft (22).

11. The linear drive (1) according to claim 1, characterized in that the camshaft (22) comprises at least two camshaft disks (24) which are arranged in parallel and spaced apart transversely to the longitudinal axis (X).

12. The linear drive (1) according to claim 11, characterized in that the at least two camshaft disks (24) are arranged at an angular offset at an angle (β) about the longitudinal axis (X).

13. The linear drive (1) according to claim 11, characterized in that the at least two camshaft disks (24) are arranged asymmetrically about the longitudinal axis (X).

14. The linear drive (1) according to claim 11, characterized in that the at least two camshaft disks (24) are designed in such a way that, when the drive shaft (20) rotates at a constant angular speed, the at least two propulsion elements (30) are pushed into and out of the rack (10) at a substantially constant speed.

15. The linear drive (1) according to claim 11, characterized in that the camshaft disk (24) has a guide means which predetermines the cyclical stroke movement during the rotation (φ) of the drive shaft (20).

16. The linear drive (1) according to claim 15, characterized in that the guide means is formed on the camshaft disk (24) at a distance (A) from the transverse axis (Y) in the direction of rotation and in that the change in the distance (A) in at least one first portion (26) increases approximately linearly in the direction of rotation and decreases linearly in the direction of rotation in at least one second portion (27).

17. The linear drive (1) claim 1, characterized in that the at least one first portion (26) and the at least one second portion (27) are connected by rounded transitions (28).

18. The linear drive (1) claim 1, characterized in that the first portion (26) extends over a first semicircle and in that the second portion (27) extends over a second semicircle.

19. The linear drive (1) claim 1, characterized in that a width (B) of the recess (40) is selected in such a way that the camshaft disk (24) is encompassed approximately without play.

20. The linear drive (1) claim 1, characterized in that a height (H) of the recess (40) is selected in such a way that the camshaft disk (24) is approximately contact-free.

21. The linear drive (1) claim 1, characterized in that each propulsion tooth (35) and/or the tooth (15) are designed to be symmetrical and to correspond.

22. The linear drive (1) claim 1, characterized in that a carriage (50) is provided, and in that the drive shaft (20) is provided in the carriage and the at least two propulsion teeth are supported by bearings.

23. The linear drive (1) according to claim 22, characterized in that the carriage (50) has at least one linear guide means (52) by which the at least two propulsion elements (30) are linearly guided in the stroke axis (Z).

24. The linear drive (1) claim 1, characterized in that a drive (60) is provided, wherein the drive (60) drives the drive shaft (20).

25. A longitudinal seat adjustment device (2) having a linear drive (1) according to claim 1.

26. A motor vehicle (3) having a linear drive (1) according to claim 1 or a longitudinal seat adjustment device (2).

Description

[0044] FIG. 1 is a greatly simplified perspective representation of a longitudinal seat adjustment device having a linear drive;

[0045] FIG. 2 is an enlarged perspective representation of the linear drive having a rack oriented in a longitudinal axis, four propulsion elements, a drive shaft, and a carriage accommodating the propulsion elements according to FIG. 1;

[0046] FIG. 3 is a simplified representation of the linear drive according to FIGS. 1 and 2, with the carriage being omitted for better understanding;

[0047] FIG. 4 is a sectional view in a plane transverse to the longitudinal axis;

[0048] FIG. 5 is a simplified sectional view of the linear drive according to FIG. 3;

[0049] FIG. 6 is a simplified perspective representation of a linear drive according to a second exemplary embodiment, with the carriage being omitted for better understanding;

[0050] FIG. 7 is a top view of the linear drive according to FIG. 6;

[0051] FIG. 8 is a sectional view of the linear drive having the carriage according to FIG. 6 in a plane transverse to the longitudinal axis;

[0052] FIG. 9 is a simplified side view of the linear drive according to the second exemplary embodiment;

[0053] FIG. 10 is a simplified perspective representation of a linear drive according to a third exemplary embodiment, with the carriage being omitted for better understanding;

[0054] FIG. 11 is a top view of the linear drive according to FIG. 10;

[0055] FIG. 12 is a sectional view of the linear drive according to the third exemplary embodiment having the carriage in a plane transverse to the longitudinal axis;

[0056] FIG. 13 is a simplified side view of the linear drive according to the third exemplary embodiment; and

[0057] FIG. 14 shows four detailed representations of the different propulsion elements of the linear drive according to the third exemplary embodiment.

[0058] Identical or functionally identical components in an exemplary embodiment are identified below with the same reference symbols. For the sake of clarity, not all parts that are the same or functionally the same in the individual figures are provided with a reference number.

[0059] FIG. 1 shows a longitudinal seat adjustment device 2 according to the invention of a motor vehicle 3 (not shown) having a linear drive 1 which is designed to adjust a seat (not shown) of the motor vehicle 3 in a longitudinal axis X.

[0060] The longitudinal seat adjustment device 2 can have a lower rail (not shown), the lower rail being connected to a chassis (not shown), and can have an upper rail (not shown) having the seat, the upper rail being movable relative to the lower rail in the longitudinal axis X.

[0061] The linear drive 1, which is shown in detail in three different exemplary embodiments in FIGS. 3-13, comprises at least one rack 10, a drive shaft 20, and at least two propulsion elements 30.

[0062] Furthermore, the linear drive 1 can comprise a carriage 50 which can support the propulsion elements 30 and the drive shaft 20 by means of bearings. The carriage 50 can be formed from two housing parts 54, 56 which can be joined together in a plane perpendicular to the longitudinal axis X.

[0063] The at least one rack 10 is arranged along the longitudinal axis X and has a plurality of teeth 15 which are lined up in the longitudinal axis X, preferably equidis-tantly. The teeth 15 can have a symmetrical tooth profile with two contact surfaces 18 formed on the flanks and a tooth space 16 formed between the teeth.

[0064] The drive shaft 20 can be driven by a drive 60, with a gear unit 65 preferably being provided between the drive 60 and the drive shaft 20, by means of which gear unit a desired step-up or step-down ratio can be brought about. The drive shaft 20 is arranged in a transverse axis Y perpendicularly to the longitudinal axis X, with the transverse axis Y and the longitudinal axis X being able to span a plane which is arranged in parallel with the rack 10.

[0065] In the exemplary embodiments described below by way of example, the linear drive 1 has four propulsion elements 30 in each case. Each propulsion element 30 comprises at least one propulsion tooth 35 and is linearly movable in a stroke axis Z which is oriented transversely to the longitudinal axis X and transversely to the drive shaft 20 or the transverse axis Y.

[0066] Each propulsion element 30 can be linearly guided in the carriage 50 by linear guide means 52 in the stroke axis Z, said guide means predetermining the position of each propulsion element 30 in the transverse axis Y and longitudinal axis X. The linear guide means 52 can, for example, support each propulsion element 30 in a V-shaped or U-shaped manner, by bearing on bearing surfaces 32 in the front end region and/or in a rear end region.

[0067] The at least one propulsion tooth 35 is designed to correspond to the teeth 15 of the rack 10 and can have a symmetrical tooth profile with two contact surfaces 38 formed on the flanks. For better understanding, the reference numerals with the suf-fixes a, b, c, and d are added for the four propulsion elements 30 in the figures below in order to identify the different movements during the cyclical stroke movement. The movements are also indicated in FIGS. 4, 8, 12 by means of arrow lines.

[0068] It can be seen from FIG. 3 that the propulsion elements 30 are arranged transversely to the longitudinal axis X, specifically in the transverse axis Y, parallel and next to or adjacent to one another.

[0069] The propulsion elements 30 are drivingly coupled to the drive shaft 20, as a result of which a rotational movement of the drive shaft 20 results in or is converted into a cyclical translational movement in the stroke axis Z. In the course of one rotation φ of the drive shaft 20, each propulsion element 30 performs at least one cyclical movement and, during the cyclical movement, enters and exits the at least one rack 10 to generate propulsion in the longitudinal axis X. This cyclical stroke movement can be described, for example, as one complete period of a sine curve, each propulsion element 30 entering the rack 10 or a tooth space 16 once, fully exiting once, and returning to the initial position within one cyclical stroke movement. However, within the meaning of this invention, it is also possible for each propulsion element 30 to perform a plurality of cyclical stroke movements during one rotation φ.

[0070] The cyclical stroke movement of the at least two propulsion elements 30 takes place with a phase shift Δφ, as a result of which the propulsion elements 30 enter or exit the rack 10 in different angular positions of the drive shaft 20. Referring to FIGS. 4 and 5, it can be seen that the propulsion elements 30a, 30b, 30c, 30d enter and exit a tooth space 16 of the rack 10 at different times when the drive shaft 20 is rotating at a constant speed. The propulsion element 30a has fully entered the rack and is at the turning point. The propulsion element 30d has fully exited the rack and is also at the turning point. The propulsion element 30b is in the cyclical stroke movement while exiting and the propulsion element 30b is in the cyclical stroke movement while entering the rack 10. In FIG. 5, these movements are indicated by means of arrow lines.

[0071] The driving coupling between the drive shaft 20 and each propulsion element is brought about by guide means, it being possible for the guide means to be in operative contact with each propulsion element 30. The guide means preferably has a friction surface which interacts with a corresponding friction surface of the propulsion element 30, the friction surface of the drive shaft 20 predetermining the position of the propulsion element 30 in the vertical axis Z. For this purpose, the corresponding friction surfaces can slide off one another, with the propulsion element 30 being deflected during the sliding motion in order to enter or exit the rack.

[0072] Referring to FIG. 5, an exemplary embodiment of the coupling between the drive shaft 20 and the relevant propulsion element 30 is shown, it being evident that the drive shaft 20 comprises a camshaft and each propulsion element 30 has a recess 40.

[0073] The camshaft 22 can be formed by a plurality of camshaft disks 24, with each propulsion element 30 preferably being assigned a camshaft disk 24. Each camshaft disk 24 is arranged for conjoint rotation with the drive shaft 20 and for mutual rotation about the transverse axis Y at an angle β. As a result, the phase shift can be realized in the cyclical stroke movement of the respective propulsion elements. In the exemplary embodiments shown, which each have propulsion elements 30, the angle β can be 90°.

[0074] According to what is shown in FIGS. 3 and 4, the drive shaft 20 passes through the propulsion elements 30 in the recess 40 and can be supported laterally, preferably on both sides of the propulsion elements 30, by bearings 58.

[0075] The recess 40—see also FIG. 13—can be designed in the manner of a through opening or through hole. The recess 40 has a maximum width B in the longitudinal axis X and a height H in a stroke axis Z. In the longitudinal axis X, the recess 40 is framed by two side surfaces 42, 43 and in the stroke axis Z by two longitudinal surfaces 44, 45. The height H is preferably at least as great as the width B and more preferably the height H is greater than the width B, i.e., H≥B.

[0076] The driving coupling between the drive shaft 20 or the camshaft 22 and the propulsion element 30 takes place in the recess 40 by an operative contact between the friction surfaces of the camshaft disk 24 and the longitudinal surfaces 44, 45 of the recess 40. By means of the coupling between the camshaft 22 and the relevant propulsion element 30, the propulsion element 30 can be pushed into and back out of the rack 10, without having to provide separate return means for this purpose. For pushing in, a force is applied by the camshaft disk 24 to the longitudinal surfaces 44 facing the rack 10 and for pushing out, a force is applied to the longitudinal surfaces 45 facing away from the rack 10.

[0077] The camshaft disk 24 is designed in such a way that, when the drive shaft 20 rotates at a constant angular speed, the at least one propulsion element 30 is pushed into and out of the rack 10 at a substantially constant speed. This produces a movement of each propulsion element 30 in the stroke axis Z that is as linear or constant as possible.

[0078] More specifically, the camshaft disk 24 is heart-shaped in the illustrated exemplary embodiment and has a first portion 26 and a second portion 27, each of which extends over a semicircle. The first portion 26 and the second portion 27 are mirror-symmetrical and have approximately the profile of a spiral. The spiral-shaped profile of each portion 26, 27 is selected in such a way that the distance between the transverse axis Y and the friction surface changes approximately constantly in a direction of rotation as the revolution angle of the camshaft disk 24 increases. With a constant rotation of the camshaft disk 24, the radius increases linearly with the rotation in the first portion 26 and the radius decreases linearly in the second portion 27. Furthermore, the radius of the two portions 26, 27 is selected in such a way that the distance between two diametrical sides of the friction surface corresponds approximately to the width B of the recess 40. As a result, when the camshaft disk 24 rotates, a center of the area of the camshaft disk 24 travels exactly in parallel with the longitudinal axis X in the transverse direction Y.

[0079] A transition 28 connecting the spiral-shaped profiles is formed between the first portion 26 and the second portion 27 in each case. The transition 28 is formed in the manner of a transition radius and, in a preferred and illustrated embodiment, can correspond approximately to the width B of the recess 40. In order to avoid wedging or jamming of the camshaft disk 24 in the recess 40, the transitions 28 can be selected in such a way that the distance between the two opposite diametrically formed transitions 28 is at least 90%, preferably more than 95%, of the width H of the recess 40.

[0080] In order to generate a corresponding propulsion when the relevant propulsion element 30 is pushed into the rack 10 or the tooth space 16 thereof, the respective contact surfaces 18, 38 of the rack 10 and the propulsion element 30 or the propulsion tooth 35 must mesh with one another in the longitudinal axis X with an offset, where the offset ΔX is directly correlated with the phase shift Δφ.

[0081] The offset ΔX— see FIG. 3—according to the exemplary embodiment in FIGS. 3-6 is accomplished by a helical gearing with a helix angle α.

[0082] The propulsion teeth 35 are all identical and also have helical gearing that corresponds to the helical gearing of the rack 10. The helix angle α of the helical gearing is predetermined by the dimensioning and number of the propulsion elements 30, where y is the distance from the geometric center in the transverse axis Y between the at least two propulsion elements 30, k is the number of propulsion elements 30, and x is the distance between two teeth 15 of the rack 10 in the longitudinal axis X:

[00004]$\alpha =\arctan \left(\frac{x.Math.\frac{k-1}{k}}{y}\right)$

[0083] The following relationship results for the offset ΔX between the respective propulsion elements 30 resulting from the helical gearing, where x is the distance between two teeth 15 of the rack 10 and k is the number of propulsion elements or n is the fraction of the phase shift:

ΔX=xk or ΔX=xn

[0084] The offset ΔX is related to the geometric center in the transverse axis Y of the relevant tooth 15 according to FIG. 3.

[0085] In the second exemplary embodiment according to FIGS. 6-9, the offset ΔX is accomplished by a plurality of racks 10, with each propulsion element 30 being assigned a rack 10′,10″,10″″, and 10″″ which the relevant propulsion element 30 can enter and exit. The racks 10′,10″,10″′, and 10″″ can be designed as individual parts or as an integral component.

[0086] The propulsion teeth 35 and the teeth 15 of the racks 10′,10″,10′″, and 10″″ have spur teeth. Otherwise, the structure and function of the linear gear unit 1 corresponds to the first exemplary embodiment.

[0087] The offset ΔX between the teeth 15 of the racks 10′,10″,10′″, and 10″″ in the longitudinal axis X according to FIGS. 7 and 9 can be described by the following relationship, where x is the distance between two teeth 15 of the rack 10 and k is the number of propulsion elements or n is the fraction of the phase shift:

ΔX=xk or ΔX=xn

[0088] The third exemplary embodiment according to FIGS. 10-14 is characterized in that the rack 10, as can be seen from FIGS. 11 and 13, has spur teeth which are continuous in the transverse axis Y. The offset ΔX is accomplished by differently configured propulsion elements 30, which are identified in the figures with the reference signs 30′,30″,30′″, 30″″.

[0089] Referring to the accompanying FIG. 14, it can be seen that, from propulsion element 30′,30″,30′″, 30″″ to propulsion element 30′,30″,30″′, 30″″, there is an offset between the propulsion teeth 35 in the transverse axis Y. The offset ΔX between the propulsion teeth 35 of the propulsion elements 30′,30″,30″′, 30″″ in the longitudinal axis X according to FIG. 14 can be described by the following relationship, where x is the distance between two teeth 15 of the rack 10 and k is the number of propulsion elements 30 or n is the fraction of the phase shift:

ΔX=xk or ΔX=xn

[0090] Otherwise, the structure of the linear drive 1 according to the third exemplary embodiment corresponds to the linear drive 1 according to the first exemplary embodiment, which was described in detail above.

[0091] At this point, for the sake of completeness, it is noted that combinations of these three exemplary embodiments are possible.

TABLE-US-00001 List of Reference Signs  1 Linear drive  2 Longitudinal seat adjustment device  3 Motor vehicle 10 Rack 15 Tooth 16 Tooth space 18 Contact surface 20 Drive shaft 22 Camshaft 24 Camshaft disk 26 First portion 27 Second portion 28 Transition 30 Propulsion element 32 Bearing surface 35 Propulsion tooth 38 Contact surface 40 Recess 42 Side surface 43 Side surface 44 Longitudinal surfaces 45 Longitudinal surface 50 Carriage 52 Linear guide means 54 Housing part 56 Housing part 58 Bearing 60 Drive 65 Gear unit i Number of cyclical stroke movements of a propulsion element during one rotation of the drive shaft k Number of propulsion elements 30 n Fraction of the phase shift x Distance between two teeth 15/35 y Distance X Longitudinal axis Y Transverse axis Z Stroke axis ΔX Offset α Helix angle β Tooth flank angle φ Rotation Δφ Phase shift