COAXIAL GEAR SET

Abstract

A coaxial gear set comprising: a crankshaft which can be rotated about an axis of rotation and has at least one connecting rod bearing; and multiple, preferably at least three, pistons, each connected to the crankshaft by means of a connecting rod and which each have a toothing with at least one tooth on a first end face facing away from the axis of rotation. The coaxial gear set also comprises: a hollow shaft having internal toothing, wherein the pistons are located inside the hollow shaft when viewed in a plane normal to the axis of rotation; and a guide unit, wherein the pistons are each linearly guided in the guide unit and can be moved back and forth parallel to a radial direction normal to the axis of rotation, as a result of which the toothings of the first end faces of the pistons can be successively brought into meshing engagement with the internal toothing and out of meshing engagement with said internal toothing.

Claims

1. A coaxial gear set (1), comprising a crankshaft (3) rotatable about an axis of rotation (2) and having at least one connecting rod bearing (4), the coaxial gear set (1) further comprising a plurality of, preferably at least three, pistons (5a, 5b, 5c) which are connected to the at least one connecting rod bearing (4) by means of a connecting rod (6a, 6b, 6c) in each case and each comprise, on a first end face (10a, 10b, 10c) facing away from the axis of rotation (3), a toothing (11a, 11 b, 11c) with at least one tooth, the coaxial gear set (1) further comprising a hollow shaft (7) with internal toothing (8), wherein the pistons (5a, 5b, 5c) are arranged inside the hollow shaft (7) when viewed in a plane normal to the axis of rotation (2), the coaxial gear set (1) further comprising a guide unit (9), wherein the pistons (5a, 5b, 5c) are each guided linearly in the guide unit (9) and can be moved back and forth parallel to a radial direction (12a, 12b, 12c) normal to the axis of rotation (2), as a result of which the toothings (11a, 11 b, 11c) of the first end faces (10a, 10b, 10c) of the pistons (5a, 5b, 5c) can be brought successively into meshing engagement with the internal toothing (8) and into a state detached from the internal toothing (8), in order to further rotate the hollow shaft (7) or the guide unit (9) about the axis of rotation (2) during the respective meshing engagement with planar contact between the respective toothing (11a, 11 b, 11c) and the internal toothing (8).

2. The coaxial gear set (1) according to claim 1, wherein the toothings (11a, 11b, 11c) of the first end faces (10a, 10b, 10c) each have a plurality of teeth, preferably three.

3. The coaxial gear set (1) according to claim 1, wherein, as viewed along the axis of rotation (2), the connecting rods (6a, 6b, 6c) are arranged one behind the other.

4. The coaxial gear set (1) according to claim 1, wherein the connecting rods (6a, 6b, 6c) lie, at least in sections, in a common plane which is normal to the axis of rotation (2).

5. The coaxial gear set (1) according to claim 4, wherein in a plane extending parallel to the axis of rotation (2) and/or comprising the axis of rotation (2), at least one, preferably at least two, of the connecting rods (6a,6b,6c) have a substantially U-shaped or J-shaped cross-section.

6. The coaxial gear set (1) according to claim 1, wherein at least two of the pistons (5a, 5b, 5c) have different diameters (13), wherein the diameters (13) are each measured in a transverse direction and the respective transverse direction is normal to the respective radial direction (12a, 12b, 12c).

7. The coaxial gear set (1) according to claim 1, wherein at least one piezoelectric element (14a, 14b, 14c) is provided at least at one of the pistons (5a, 5b, 5c), preferably at all pistons (5a, 5b, 5c), in order to change a length (15) of the respective piston (5a, 5b, 5c) measured parallel to the respective radial direction (12a, 12b, 12c).

8. The coaxial gear set (1) according to claim 1, wherein the pistons (5a, 5b, 5c) each have, on a second end face (16a, 16b, 16c) opposite the first end face (10a, 10b, 10c), a toothing (17a, 17b,17c) having at least one tooth, in that an inner ring (18) mounted rotatably about the axis of rotation (2) is provided with external toothing (19), wherein the guide unit (9) is arranged at least in sections between the inner ring (18) and the hollow shaft (7), wherein the toothings (17a, 17b, 17c) of the second end faces (16a, 16b, 16c) of the pistons (5a, 5b, 5c) can be brought successively into meshing engagement with the external toothing (19) and into a state detached from the external toothing (19) in order to further rotate the inner ring (18) or the guide unit (9) about the axis of rotation (2) during the respective meshing engagement with planar contact between the respective toothing (17a, 17b, 17c) and the external toothing (19).

9. The coaxial gear set (1) according to claim 8, wherein the internal toothing (8) of the hollow shaft (7) and the external toothing (19) of the inner ring (18) have the same number of teeth.

10. The coaxial gear set (1) according to claim 1, wherein in at least two of the pistons (5a,5b,5c) the respective radial directions (12a,12b,12c) enclose an angle (20) measured about the axis of rotation (2) other than zero.

11. The coaxial gear set (1) according to claim 1, wherein the crankshaft (3) is of hollow design.

12. The coaxial gear set (1) according to claim 1, wherein the guide unit (9) is arranged immovable relative to the axis of rotation (2).

13. The coaxial gear set (1) according to claim 1, wherein the guide unit (9) is rotatably mounted about the axis of rotation (2), wherein means are preferably provided for braking a rotation of the guide unit (9) about the axis of rotation (2).

Description

BRIEF DESCRIPTION OF THE FIGURES

[0055] The invention will now be explained in more detail with reference to exemplary embodiments. The drawings are exemplary and are intended to illustrate the idea of the invention, but in no way to restrict it or even to reproduce it conclusively, wherein:

[0056] FIG. 1 shows a schematic sectional view of a coaxial gear set according to the invention, wherein connecting rods are arranged one behind the other as seen along an axis of rotation;

[0057] FIG. 2 shows a sectional view according to sectional line A-A of FIG. 1, wherein the arrows indicate the direction of view;

[0058] FIG. 3 shows a schematic sectional view of a further embodiment of the coaxial gear set according to the invention, wherein the connecting rods lie, at least in sections, in a common plane which is normal to the axis of rotation;

[0059] FIG. 4 shows a sectional view according to sectional line B-B of FIG. 3, wherein the arrows indicate the direction of view;

[0060] FIG. 5 shows a schematic sectional view of a further embodiment of the coaxial gear set according to the invention analogous to the embodiment of FIG. 3, wherein toothings of first end faces of pistons have several teeth;

[0061] FIG. 6 shows a schematic sectional view of a further embodiment of the coaxial gear set according to the invention analogous to the embodiment of FIG. 1, wherein the pistons comprise piezo elements;

[0062] FIG. 7 shows a schematic sectional view of a further embodiment of the coaxial gear set according to the invention analogous to the embodiment of FIG. 1, wherein an inner ring with external toothing is provided.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0063] In FIG. 1, a schematic view of a section normal to an axis of rotation 2 shows a coaxial gear set 1 or crankshaft transmission according to the invention. The coaxial gear set 1 comprises a crankshaft 3 rotatable about the axis of rotation 2 and having at least one connecting rod bearing 4, wherein in the illustrated exemplary embodiment exactly one connecting rod bearing 4 or exactly one crank journal or crank pin is provided.

[0064] Several pistons are connected to the connecting rod bearing 4 in a manner known per se or the pistons are movably mounted on the connecting rod bearing 4, e.g. in each case a divided connecting rod eye of connecting rods 6a, 6b, 6c is fastened to the connecting rod bearing 4 by means of screws 21, cf. FIG. 1, and pistons 5a, 5b, 5c are connected to further connecting rod eyes of the connecting rods 6a, 6b, 6c via piston pins. In the exemplary embodiment of FIG. 1, a total of five pistons are provided, although only the three pistons 5a, 5b, 5c are visible in FIG. 1. The piston 5a is connected to the crankshaft 3 or the connecting rod bearing 4 via the connecting rod 6a, the piston 5b via the connecting rod 6b and the piston 5c via the connecting rod 6c.

[0065] All of the pistons 5a, 5b, 5c each have a first end face 10a, 10b, 10c facing away from the axis of rotation 2 and having an imprinted toothing 11a, 11b, 11c, wherein the respective toothing 11a, 11b, 11c comprises exactly one tooth in the exemplary embodiment shown.

[0066] In the illustrated exemplary embodiment, as can be seen from FIG. 1, the crankshaft 3 is hollow along the axis of rotation 2, which allows, for example, cables (not shown) to be passed through without twisting.

[0067] Furthermore, a hollow shaft 7 is provided in the coaxial gear set 1, which has an internal toothing 8. In the image plane of FIG. 1, which is perpendicular to the axis of rotation 2, the pistons 5a, 5b, 5c—and at least in sections the crankshaft 3—are arranged inside the hollow shaft 7. This also applies to a guide unit 9 in which the pistons 5a, 5b, 5c are each guided linearly and can be moved back and forth parallel to a radial direction 12a, 12b, 12c which is perpendicular to the axis of rotation 2. For this purpose, the guide unit 9 in the illustrated exemplary embodiment has hollow cylinders which act as linear guides for the pistons 5a, 5b, 5c.

[0068] As a result of the reciprocating movement of the pistons 5a, 5b, 5c, the toothings 11a, 11b, 11c of the first end faces 10a, 10b, 10c of the pistons 5a, 5b, 5c are successively brought into meshing engagement with the internal toothing 8 and into a state disengaged from the internal toothing 8, wherein, due to the linear movement of the pistons 5a, 5b, 5c during the respective engagement, a planar contact between the respective toothing 11a, 11b, 11c and the internal toothing 8 can be ensured and the respective toothing 11a, 11b, 11c presses planarly against the internal toothing 8. As a result, the hollow shaft is rotated a little further about the axis of rotation 2 if the guide unit 9 is arranged immovably relative to the axis of rotation 2 or if the guide unit 9 is arranged rotatably about the axis of rotation 2 but is braked. If, on the other hand, the hollow shaft 7 is fixed or immovable with respect to the axis of rotation 2 or is braked, the guide unit 9 (which is rotatably mounted about the axis of rotation 2) is rotated a little further. Due to the two-dimensional engagement or pressing, very high torques can be transmitted from the crankshaft 3 to the hollow shaft 7 or, optionally, the guide unit 9.

[0069] In the exemplary embodiment of FIG. 1, the connecting rods 6a, 6b, 6c are arranged one behind the other on the crankshaft 3 or the connecting rod bearing 4 as seen along the axis of rotation 2. This is illustrated in the sectional view of FIG. 2 (according to the sectional line A-A of FIG. 1, wherein the arrows indicate the direction of view), in which a fourth piston 5c′ and an associated connecting rod 6c′ as well as a connecting rod 6a′ of a fifth piston (not shown, this piston, as viewed in the direction of the drawing plane of FIG. 1, lies behind the elements shown in FIG. 1 or, as viewed along the axis of rotation 2, is the last piston, the piston 5a being the first) can also be seen.

[0070] In order to ensure effective and at the same time space-saving mass balancing, in particular for relatively high speeds, different piston diameters 13 are provided in the exemplary embodiment shown in FIG. 1, wherein the piston diameters 13 are each measured in a transverse direction and the respective transverse direction is normal to the respective radial direction 12a, 12b, 12c. Specifically, the piston 5b has a larger piston diameter 13 than the pistons 5a and 5b, with all the pistons except the piston 5b having the same piston diameter 13 (therefore, for clarity, the piston diameter 13 of the piston 5a is not specially drawn in FIG. 1).

[0071] It should be noted that in the illustrated exemplary embodiment, the pistons 5a, 5b, 5c have a circular cross-section in sections arranged in the hollow cylinders of the guide unit 9, wherein the respective cross-section lies in a plane normal to the respective radial direction 12a, 12b, 12c.

[0072] As can also be seen from FIG. 1 and FIG. 2, some pistons 5a, 5b, 5c have an angular offset 20 from each other measured about the axis of rotation 2. This means that the radial directions 12a, 12b, 12c associated with the respective pistons 5a, 5b, 5c each enclose with each other a non-zero angle measured about the axis of rotation 2. Specifically, in the illustrated exemplary embodiment, the angular offset 20 between the piston 5a and the piston 5b or the angle between the radial direction 12a and the radial direction 12b is 120°. Analogously, the angular offset 20 between the piston 5b or 5c and the piston 5c or 5a or the angle between the radial direction 12b or 12c and the radial direction 12c or 12a is 120°.

[0073] The piston 5c′ is arranged at the same angular position around the axis of rotation 2 as the piston 5c, cf. FIG. 2. The fifth piston (not shown) is arranged at the same angular position around the axis of rotation 2 as the piston 5a.

[0074] The angular offset 20 may cause teeth of the internal toothing 8 to be skipped depending on the angle of the pistons 5a, 5b, 5c with respect to each other and/or may change the direction of rotation of the hollow shaft 7 or, optionally, of the guide unit 9. This means that the behavior of the coaxial gear set 1 may be influenced by the angular offset 20.

[0075] FIG. 3 shows a schematic sectional view of a further embodiment of the coaxial gear set 1 according to the invention with exactly three pistons 5a, 5b, 5c and three associated connecting rods 6a, 6b, 6c, wherein the connecting rods 6a, 6b, 6c, as viewed along the axis of rotation 2, do not lie one behind the other but lie, at least in sections, in a common plane which is normal to the axis of rotation 2. This embodiment has a correspondingly extremely compact construction, since the dimensioning parallel to the axis of rotation 2 can be kept correspondingly short.

[0076] The pistons 5a, 5b, 5c in the exemplary embodiment of FIG. 3 have the same piston diameter 13. Mass balancing can, for example, be carried out in a manner known per se by means of balancing weights on the crankshaft 3.

[0077] As can be seen from the sectional view of FIG. 4 (according to the sectional line B-B of FIG. 3, wherein the arrows indicate the direction of view), this arrangement of the connecting rods 6a, 6b, 6c “one above the other” is made possible by the fact that the connecting rods 6a and 6c have a substantially U-shaped cross-section in a plane parallel to the axis of rotation 2 and/or comprising the axis of rotation 2. The connecting rod 6b has a substantially I-shaped cross-section, as seen along the axis of rotation 2, arranged between those sections of the connecting rod 6c which form the two parallel legs of the U-shape of the cross-section of the connecting rod 6c. Said sections of the connecting rod 6c, as seen along the axis of rotation 2, are in turn arranged between those sections of the connecting rod 6a which form the two parallel legs of the U-shape of the cross-section of the connecting rod 6a.

[0078] Otherwise, the same applies to the embodiment of FIG. 3 as to the embodiment of FIG. 1. In particular, the pistons 5a, 5b, 5c of the embodiment of FIG. 3 also have a mutual angular offset 20 of 120°.

[0079] In order to further increase the magnitude of the transmittable torques, the toothings 11a, 11b, 11c may each have a plurality of teeth. Such an exemplary embodiment is illustrated in FIG. 5, which otherwise corresponds to that exemplary embodiment of FIG. 3. Specifically, in the exemplary embodiment of FIG. 5, the toothings 11a, 11b, 11c each have three teeth, whereby the amount of transmittable torque can be significantly increased compared to the exemplary embodiment of FIG. 3.

[0080] FIG. 6 shows a schematic sectional view of a further embodiment of the coaxial gear set 1 according to the invention analogous to the embodiment of FIG. 1, wherein the pistons 5a, 5b, 5c have piezo elements 14a, 14b, 14c. By means of the piezo elements 14a, 14b, 14c, a piston length 15 (drawn in FIG. 6 only for the piston 5b for reasons of clarity) of the respective piston 5a, 5b, 5c measured parallel to the respective radial direction 12a, 12b, 12c can be changed. In this way, an expansion in length of the pistons 5a, 5b, 5c due to heat or wear can be compensated. Furthermore, by increasing the piston length 15 by means of the piezo elements 14a, 14b, 14c, an increased contact pressure, in particular of the toothings 11a, 11b, 11c of the first end faces 10a, 10b, 10c on the internal toothing 8, can be achieved.

[0081] Provided that the pistons 5a, 5b, 5c also each have an impressed toothing 17a, 17b, 17c on a second end face 16a, 16b, 16c opposite the first end face 10a, 10b, 10c, a contact pressure can optionally also be increased there by means of the piezo elements 14a, 14b, 14c.

[0082] An embodiment in which the pistons 5a, 5b, 5c have second end faces 16a, 16b, 16c with toothings 17a, 17b, 17c is shown in FIG. 7. This embodiment also has an inner ring 18 and is otherwise analogous to the embodiment of FIG. 1. Accordingly, reference is made in principle to what has been said above about the embodiment of FIG. 1.

[0083] In the illustrated exemplary embodiment, the toothings 17a, 17b, 17c each have one tooth, but multiple teeth per toothing 17a, 17b, 17c are possible.

[0084] The inner ring 18 has an external toothing 19 facing the internal toothing 8 and is mounted rotatably about the axis of rotation 2. The guide unit 9 is arranged at least in sections between the inner ring 18 and the hollow shaft 7, wherein the toothings 17a, 17b, 17c of the second end faces 16a, 16b, 16c of the pistons 5a, 5b, 5c can be brought successively into meshing engagement with the external toothing 19 and into a state detached from the external toothing 19.

[0085] During the respective engagement, due to the linear movement of the pistons 5a, 5b, 5c, a planar contact between the respective toothing 17a, 17b, 17c and the external toothing 19 of the inner ring 18 can be ensured and can press the respective toothing 17a, 17b, 17c in a planar manner against the external toothing 19.

[0086] As a result, the inner ring 18 is rotated a little further about the axis of rotation 2 when the guide unit 9 is arranged immovable relative to the axis of rotation 2 or when the guide unit 9 is arranged rotatable about the axis of rotation 2 but is braked. More precisely, when the guide unit 9 is braked or fixed, one or each piston 5a, 5b, 5c alternately drives the hollow shaft 7 and the inner ring 18. Thus, both the inner ring 18 and the hollow shaft 7 can act as an output.

[0087] It is also possible for only the hollow shaft 7 or the inner ring 18 to act as an output, in which case the other element is braked or locked.

[0088] It would of course also be conceivable that both the hollow shaft 7 and the inner ring 18 are fixed, so that only the guide unit 9 is moved and can act as an output drive.

[0089] In particular, in contrast to solutions with linear contact, very high torques can be transmitted between the crankshaft 3 and the inner ring 18 or, optionally, the guide unit 9.

[0090] In the exemplary embodiment of FIG. 7, the external toothing 19 has exactly the same number of teeth as the internal toothing 8. The geometries or contours of the internal toothing 8 and the external toothing 19 are accordingly designed differently, i.e. with comparatively larger teeth or tooth spacings of the internal toothing 8 of the hollow shaft 7. Accordingly, the hollow shaft 7 and the inner ring 18 rotate at the same angular velocity. The latter can also be achieved by a rotationally fixed connection of the hollow shaft 7 to the inner ring 18.

[0091] Since the inner ring 18 has a smaller diameter than the hollow shaft 7, lower tangential speeds can be achieved or tapped at this at the same angular speeds.

[0092] This means that the inner ring 18 and the hollow shaft 7 can provide two output drives for different speeds at the same time, which means that a second gear set can be saved depending on the application.

LIST OF REFERENCE SIGNS

[0093] 1 Coaxial gear set [0094] 2 Axis of rotation [0095] 3 Crankshaft [0096] 4 Connecting rod bearing [0097] 5a, 5b, 5c, 5c′ Piston [0098] 6a, 6a′, 6b, 6c, 6c′ Connecting rod [0099] 7 Hollow shaft [0100] 8 Internal toothing of the hollow shaft [0101] 9 Guide unit [0102] 10a, 10b, 10c First end face of piston [0103] 11a, 11b, 11c Toothing on the first end face [0104] 12a, 12b, 12c Radial direction [0105] 13 Piston diameter [0106] 14a, 14b, 14c Piezo element [0107] 15 Piston length [0108] 16a, 16b, 16c Second end face of piston [0109] 17a, 17b, 17c Toothing on the second end face [0110] 18 Inner ring [0111] 19 External toothing of the inner ring [0112] 20 Angular offset [0113] 21 Screw