Coaxial transmission

Abstract

A coaxial transmission device (1), comprising: a crankshaft (3) rotatable about a rotation axis (2) and having at least one crank pin (4); at least one piston group, the piston group having a plurality of pistons (5a-i), each of which has a toothing (11) with at least one tooth on a first end side (10) remote from the rotation axis; a hollow shaft (7) having an internal toothing (8), wherein the piston is arranged in the hollow shaft when viewed in a plane perpendicular to the rotation axis; and a guide unit (9), wherein the pistons are linearly guided in the guide unit and can reciprocate parallel to a radial direction perpendicular to the rotation axis, whereby the toothing of the first end side of the piston can be placed in a state of meshing with the internal toothing and in a state of disengagement from the internal toothing in turn. According to the present invention, in order to connect the pistons of the corresponding piston group to at least one crank pin, a common connecting rod (6) constructed in a star shape is respectively provided, and the pistons of the corresponding piston group are coupled to the connecting rod.

Description

Technical Field

[0001] The present invention relates to a coaxial transmission device, which includes a crankshaft rotatable about a rotation axis and having at least one crank pin. In addition, the coaxial transmission device includes at least one piston group, which has a plurality of, preferably at least three, pistons, each of which has a toothing with at least one tooth on a first end side away from the rotation axis. The coaxial transmission device also includes a hollow shaft with an internal toothing, wherein the piston is arranged in the hollow shaft when viewed in a plane perpendicular to the rotation axis. In addition, the coaxial transmission device includes a guide unit, wherein the pistons are respectively linearly guided in the guide unit and can reciprocate parallel to a radial direction perpendicular to the rotation axis, whereby the toothing on the first end side of the piston can be placed in a state of meshing with and disengaging from the internal toothing in sequence, so that during the corresponding meshing, preferably with surface contact between the corresponding toothing and the internal toothing, the hollow shaft or the guide unit can continue to rotate about the rotation axis. Background Art

[0002] A crankshaft or coaxial transmission is known from AT 521617Bl, which includes a crankshaft rotatable about an axis of rotation and having at least one connecting rod bearing or crank pin, and further includes a plurality of, for example, three pistons, each of which is connected to at least one crank pin by means of a connecting rod and each of which has a toothing with at least one tooth on a first end side remote from the axis of rotation. In addition, the coaxial transmission includes a hollow shaft with an internal toothing, wherein the piston is arranged in the hollow shaft when viewed in a plane perpendicular to the axis of rotation. In addition, the coaxial transmission includes a guide unit, wherein the piston is linearly guided in the guide unit and can reciprocate parallel to a radial direction perpendicular to the axis of rotation, whereby the toothing on the first end side of the piston can be placed in a state of meshing with the internal toothing and a state of disengagement from the internal toothing in sequence, so that during the corresponding meshing period, with surface contact between the corresponding toothing and the internal toothing, the hollow shaft or the guide unit continues to rotate about the axis of rotation. With this coaxial transmission, high torques can be transmitted while taking up a small amount of space, wherein high transmission ratios and high precision, or rather play-freeness, can be achieved. In order to achieve the most uniform introduction of force possible, a greater number of pistons are required, but this is accompanied by a corresponding increase in the overall length of the coaxial transmission measured parallel to the axis of rotation, which can prove to be disadvantageous depending on the application.

[0003] Furthermore, due to the increase in the number of components, the complexity of the system increases accordingly, which is also considered disadvantageous with regard to deviations due to manufacturing tolerances. Summary of the invention

[0004] The object of the present invention is to provide an improved coaxial or crankshaft transmission which overcomes the above-mentioned disadvantages.

[0005] In order to achieve the above object, a coaxial transmission device is provided, which comprises a crankshaft rotatable about a rotation axis and having at least one crank pin. In addition, the coaxial transmission device comprises at least one piston group, the piston group having a plurality of, preferably at least three, pistons, each of which has a toothing with at least one tooth on a first end side away from the rotation axis. The coaxial transmission device also comprises a hollow shaft with an internal toothing, wherein the piston is arranged in the hollow shaft when viewed in a plane perpendicular to the rotation axis. The coaxial transmission device also comprises a guide unit, wherein the pistons are respectively linearly guided in the guide unit and can be parallel to each other. In radial reciprocating motion perpendicular to the axis of rotation, the toothed portion on the first end side of the piston can be placed in a state of engagement with the internal toothed portion and a state of disengagement from the internal toothed portion in sequence, so that during the corresponding engagement, preferably with surface contact between the corresponding toothed portion and the internal toothed portion, the hollow shaft or guide unit continues to rotate around the axis of rotation. According to the present invention, in order to connect the pistons of the corresponding piston group with at least one crank pin, a common, star-shaped connecting rod is respectively provided, and the pistons of the corresponding piston group are coupled to the connecting rod, so that the pistons of the corresponding piston group can be prevented from being offset relative to each other along the axis of rotation.

[0006] That is to say, a connecting rod configured in a star shape is provided for each piston group, which is also referred to as a "star connecting rod" below. Another possible name for a connecting rod configured in a star shape is a "star connector". Accordingly, pistons connected to a common, more precisely the same, star connecting rod are classified as a "piston group".

[0007] Each star connecting rod can be provided with its own crank pin; however, in theory, it is also possible to equip each crank pin with multiple star connecting rods, so that, with compact dimensions of the coaxial transmission, more pistons can be provided as a whole to further increase or improve uniformity, torque capacity and force transmission. The corresponding crank pin can also be called a connecting rod journal.

[0008] The crank pin is an eccentric. Therefore, within the scope of the present invention, the crank pin can also be properly referred to as the eccentric of the eccentric shaft. Therefore, within the scope of the present invention, "crankshaft" is also understood to be "eccentric shaft" in principle, and vice versa, without taking into account the fact that the eccentric shaft is usually supported in a cantilevered manner, while the crankshaft is usually supported on both sides.

[0009] By arranging a plurality of spiders one behind the other on different crank pins, viewed along the axis of rotation, other, more precisely lower transmission ratios can in turn be realized in a simple manner.

[0010] The spider is used - like any common connecting rod, sometimes also called a "push rod" - to convert the rotation of the crankshaft into a linear movement of the piston, wherein the spider - in contrast to the crank pin forming the eccentric - does not rotate itself in a plane perpendicular to the axis of rotation relative to the guide unit (about the axis of rotation), but rather performs an orbital movement in this plane. This orbital movement in the plane perpendicular to the axis of rotation is caused by the eccentricity and can be regarded as a parallel movement relative to the guide unit, which is superimposed to a certain extent on the movement in the form of a rocking motion.

[0011] Here, the spider not only causes the "forward stroke", that is to say the movement of the piston in the direction of the internal toothing of the hollow shaft, but also the so-called "return stroke", that is to say the movement of the piston away from the internal toothing of the hollow shaft. The fact that the piston is also pulled back again (return stroke) by means of the spider can be considered an important advantage compared to solutions without connecting rods. This makes it possible, in particular, to realize virtually any installation position of the coaxial transmission, since there is no risk that a piston which is not meshing with the internal toothing falls back due to gravity and thus meshes with the internal toothing again unintentionally.

[0012] Although the solution with cams can also prevent the fall back, it is necessary to realize multiple eccentricity of the cam, thereby generating a cam cross section different from a circle (polygonality of the cam). The disadvantage here is that the possible transmission ratio is reduced (transmission ratio i = number of teeth / number of edges; correspondingly, the transmission ratio is halved when the number of edges is 2, and the transmission ratio is reduced to one third when the number of edges is 3, etc.). In other words, the star connecting rod also overcomes the disadvantage of reduced transmission ratio.

[0013] Furthermore, in the coaxial transmission according to the invention, no sliding of the cam on the sliding surface of the corresponding piston facing the cam also occurs. This is also advantageous, because in order to optimize this sliding, it is usually necessary to design the sliding surface of the piston very smoothly (which is again considered to be restrictive), but this is not necessary at all in the coaxial transmission according to the invention.

[0014] By providing only a single, star-shaped connecting rod for all pistons of a piston group, the overall length of a coaxial or crankshaft drive measured parallel to the axis of rotation can be significantly reduced, since the pistons can be arranged essentially without offset relative to one another when viewed along the axis of rotation. Of course, a certain offset cannot be excluded in theory, which may occur, for example, due to manufacturing tolerances. In addition, a slight offset may also be intentionally provided, for example again for manufacturing reasons.

[0015] In any case, the number of components is correspondingly reduced, since each piston does not have to be provided with its own connecting rod, which reduces the complexity of the system and thus has a positive effect on deviations due to manufacturing tolerances.

[0016] Thus, by virtue of the fact that a large number of pistons can be used without any problems, on the one hand a particularly uniform introduction of force is achieved and on the other hand extremely high torques can be transmitted.

[0017] Furthermore, the following also applies to the coaxial transmission or crankshaft transmission according to the invention:

[0018] The crankshaft is a drive element, or may be referred to as a drive element.

[0019] Preferably, the crankshaft is arranged at least partially within the hollow shaft, viewed in a plane perpendicular to the axis of rotation.

[0020] Preferably, the hollow shaft is mounted so that it can rotate about an axis of rotation and can serve as an output element.

[0021] Alternatively, the guide unit can be used as an output element when the hollow shaft is fixed, for which purpose the guide unit must be rotatably mounted.

[0022] In order that the hollow shaft or, if necessary, the guide unit can continue to rotate in a certain direction, at least three pistons are preferably provided. For example, an integer multiple N of 3, for example 9 (that is, for N=3), can be selected, but in principle the exact number is not subject to any restrictions and does not have to be an integer multiple of 3. The exact number can be adjusted according to the respective application, in particular with regard to the desired efficiency, and according to the system preload that is important for the starting torque of the coaxial transmission.

[0023] The further rotation is achieved by the toothing of the first end side of at least one piston pressing, in particular flatly, against the internal toothing of the hollow shaft, while at the same time the other piston exerts little or no pressing force on the internal toothing.

[0024] The piston characteristics related to how many pistons mesh with the internal toothing when and to what extent can be designed in a very variable manner. In the case of 3N pistons, it can be provided, for example, that N pistons mesh with the internal toothing and press against it. The remaining 2N pistons do not exert any pressing force on the internal toothing during this period or only exert a low pressing force. Preferably, at least 1N of the remaining 2N pistons partially mesh with the internal toothing to achieve a gap-free state. Preferably, at least one of the remaining pistons does not contact the internal toothing at all.

[0025] It should be noted that by correspondingly designing the coaxial transmission according to the invention, the exact number of pistons which mesh or partially mesh with the internal toothing can be varied in practically any manner in order to ensure freedom from play.

[0026] Generally, in the case of a plurality of pistons, the absence of play can be ensured by at least two pistons simultaneously at least partially meshing with the internal toothing, wherein preferably one of the two pistons is in an advance stroke and the other in a return stroke.

[0027] This operating principle results in very large transmission ratios.

[0028] As described above, a surface contact is achieved between the toothing of the corresponding first end side and the internal toothing of the hollow shaft. This presupposes a linear movement of the piston. In addition, the geometry of the toothing and the internal toothing can be designed or optimized accordingly to further increase the pressing or more precisely the surface contact - and thus increase the transmission of high torques -. By means of the surface pressing or surface contact between the toothing of the corresponding first end side and the internal toothing of the hollow shaft, relatively very high torques can be transmitted from the crankshaft to the hollow shaft or, if necessary, to the guide unit, compared to the solutions with line contact or linear engagement known from the prior art. In addition, the Hershel pressure is reduced by means of the surface pressing or surface contact, thereby extending the service life.

[0029] It should be noted that in the coaxial transmission here the geometry of the toothing or internal toothing can also be designed such that despite the linear movement of the piston a line contact occurs, which can be advantageous if one wants to reduce friction (and thus increase efficiency).

[0030] By means of the simple solution of increasing the number of pistons, in this case too, a further possibility of increasing the size of the transmittable torque is obtained.

[0031] By means of at least three pistons, it can be ensured that the next piston, which presses with its first end-side toothing, in particular in a flat manner, against the inner toothing, does not rotate the hollow shaft or the guide unit in the opposite direction, but only causes the hollow shaft or the guide unit to oscillate back and forth about the axis of rotation. In contrast, this situation cannot be ruled out in the case of two pistons, but additional elements (e.g. brakes or freewheels that only allow the hollow shaft or the guide unit to rotate in a certain direction) can be provided in the two pistons, so that further rotation of the hollow shaft or the guide unit can be achieved with only two pistons.

[0032] The toothing of the first end face can also be referred to as a toothing impressed on the first end face. The corresponding piston can also be referred to as a “tooth element” accordingly.

[0033] The guide unit can be designed in one piece or composed of a plurality of elements.

[0034] Due to the linear guidance of the piston in the guide unit, the piston can in each case only be moved linearly parallel to the respective radial direction, wherein the radial direction associated with the respective piston is defined by the guide unit.

[0035] The linear guide can be formed in particular by a hollow cylinder in the guide unit, in which the piston is arranged. In this case, the radial direction associated with the corresponding piston is defined by the corresponding cylinder axis. Here, the piston typically has a substantially circular cross-section (perpendicular to the corresponding radial direction). In principle, however, other piston cross-sectional shapes are also feasible, such as a rectangular or slotted cross-section, in particular in order to be able to increase the "depth" of the toothing (that is, its dimension parallel to the axis of rotation) and thereby increase the transmittable force. It should also be noted that a situation in which the guide unit is not fixed but can rotate is also feasible. As a result, the radial direction associated with the piston changes accordingly due to the rotation of the guide unit, or mathematically strictly speaking, there are an infinite number of radial directions when observed within the time period in which the guide unit rotates.

[0036] Furthermore, due to the high transmission ratio and the friction in the tooth contact, the coaxial transmission is in principle also self-locking in the event of a drive failure. In particular, the coaxial transmission can be locked by one of the pistons being left in top dead center (i.e., at the maximum forward stroke of the piston, in the corresponding radial direction away from the axis of rotation), thereby achieving the function of a brake. This type of locking is usually not possible with solutions without connecting rods.

[0037] Another advantage of a coaxial transmission is that high dynamics can be achieved, since at least one crank pin of the crankshaft performs a circular movement about the axis of rotation and preferably itself has a circular cross-section perpendicular to the axis of rotation, so that mass balancing can be achieved very simply, for example in a known manner with the aid of balancing weights or holes on the crankshaft.

[0038] In a preferred embodiment of the coaxial transmission according to the invention, it is provided that a plurality of piston groups are provided, wherein a common, star-shaped connecting rod is provided for each piston group, to which the pistons of the respective piston group are coupled. This allows the uniformity of the force transmission and the magnitude of the transmittable torque to be further increased without having to increase the overall length too much.

[0039] In order to exclude (rotational) rotations of the star-shaped connecting rod relative to the guide unit other than the orbital movement explained above in a particularly simple manner in terms of construction, in a preferred embodiment of the coaxial transmission device according to the invention, it is provided that at least two guide pins are provided to ensure the orbital movement and prevent any other rotations of the corresponding star-shaped connecting rod relative to the guide unit, which guide pins are rigidly connected to the corresponding star-shaped connecting rod and engage with at least one corresponding recess of at least one guide section which is arranged so as to be non-movable relative to the guide unit.

[0040] Preferably, a respective recess is assigned to each guide pin.

[0041] The at least one guide section may be a substantially separate component with respect to the guide unit. Alternatively, the at least one guide section may be a part of the guide unit and / or may be constructed in one piece with the guide unit.

[0042] In this case, at least two guide pins can be arranged in the guide unit, viewed in a plane perpendicular to the axis of rotation, which results in a particularly compact arrangement.

[0043] Of course, the size of at least one corresponding recess can be adjusted according to the eccentricity of the crank pin or crank. For example, if a corresponding recess is provided for each guide pin, the corresponding corresponding recess can be designed as a hole with a corresponding matching diameter, in particular by selecting the size of the hole diameter to be the eccentricity plus twice the diameter of the guide pin. Accordingly, the corresponding guide pin is always in tangential contact with the associated recess or guide section.

[0044] In order to minimize friction losses between the guide pin and the recess or guide section, a particularly preferred embodiment of the coaxial transmission according to the invention provides that rollers are provided on the guide pins for making it easier to roll on the at least one guide section when the guide pin moves in the at least one corresponding recess. That is, the corresponding guide pin does not slide on the guide section, but rolls on the at least one guide section by means of one or more rollers.

[0045] In principle, the coupling between the piston and the star-shaped connecting rod can be realized in different ways. In order to realize a coupling that is particularly simple in structure, in a preferred embodiment of the coaxial transmission according to the invention, it is provided that, in order to couple the piston of the corresponding piston group with the associated star-shaped connecting rod, an elongated hole extending transversely to the corresponding radial direction is provided in the piston, wherein a coupling pin engaging with the elongated hole is fastened to the star-shaped connecting rod.

[0046] This type of coupling has proven to be particularly space-saving, so that the crankshaft can have a correspondingly large diameter, which is not only advantageous with regard to mechanical stability, but also allows particularly much space to be available for, in particular, the torsion-free routing of cables, etc., in the case of a hollow crankshaft.

[0047] Preferably, the elongated hole extends perpendicularly to the radial direction of the corresponding piston. However, it is also conceivable that the direction of the corresponding elongated hole is not straight, but has a curvature.

[0048] Preferably, the coupling pin extends precisely with its longitudinal axis parallel to the axis of rotation.

[0049] The coupling pin is arranged in the slotted hole of the piston, so that the engagement is achieved. Thus, the movement of the piston is achieved according to the principle of a crank slider.

[0050] In a particularly preferred embodiment of the coaxial transmission according to the invention, it is provided that at least one of the coupling pins also forms at least one guide pin. This further reduces the number of parts, which saves space, weight and costs. Preferably, at least two of the coupling pins form at least two guide pins. Particularly preferably, all guide pins are formed by coupling pins.

[0051] In order to achieve an alternative, structurally simple coupling between the piston and the star-shaped connecting rod, a preferred embodiment of the coaxial transmission according to the invention provides that, in order to couple the pistons of the respective piston group with the associated star-shaped connecting rod, substantially rigid intermediate elements are provided, wherein each intermediate element is articulated on the one hand with the associated piston and on the other hand with the star-shaped connecting rod. This makes it possible to achieve particularly low-friction movements of the star-shaped connecting rod, thereby minimizing power losses.

[0052] The articulated connection between the corresponding intermediate element and the attached piston can for example be realized in a known manner by means of a swivel joint or a solid joint. For the articulated connection between the corresponding intermediate element and the attached connecting rod configured to be star-shaped, for example, a swivel joint or a solid joint can also be set respectively.

[0053] In a particularly preferred embodiment of the coaxial transmission according to the invention, it is provided that for the articulated connection between the respective intermediate element and the associated connecting rod configured in a star shape, connecting bolts are provided, wherein at least one of the connecting bolts also forms a guide pin. This reduces the number of parts, which saves space, weight and costs. Preferably, at least two of the connecting bolts form at least two guide pins. Particularly preferably, all guide pins are formed by the connecting bolts.

[0054] In order to further increase the magnitude of the transmittable torque, in a preferred embodiment of the coaxial transmission according to the present invention, it is provided that the toothing of the first end side has a plurality of teeth, preferably three teeth. As the number of teeth of the toothing of the first end side increases, the area over which the corresponding piston can press against the inner toothing becomes larger, which enables a particularly large torque to be transmitted between the crankshaft and the hollow shaft or, if necessary, the guide unit.

[0055] In a preferred embodiment of the coaxial transmission according to the invention, it is provided that the crankshaft is designed to be hollow in order to be able to guide the cable through the crankshaft, preferably in a rotationally fixed manner along the axis of rotation.

[0056] In a preferred embodiment of the coaxial transmission according to the invention, it is provided that the piston has a toothing with at least one tooth on a second end side opposite to the first end side, and an inner ring with an external toothing is provided which is supported in a manner rotatable about a rotation axis, wherein a guide unit is at least partially arranged between the inner ring and the hollow shaft, wherein the toothing on the second end side of the piston can be placed in a state of meshing with the external toothing and a state of disengagement from the external toothing in sequence, so that during the corresponding meshing, preferably with surface contact between the corresponding toothing and the external toothing, the inner ring or the guide unit continues to rotate about the rotation axis.

[0057] The toothing on the second end side may also be referred to as toothing impressed onto the second end side.

[0058] The inner ring is preferably mounted rotatably about the axis of rotation and, as long as it is not locked, has in principle the function of a shaft and can therefore also be referred to as an inner shaft. The outer toothing of the inner ring faces the inner toothing of the hollow shaft.

[0059] In principle, what has been described for the meshing of the first end-side toothing in the internal toothing of the hollow shaft applies analogously to the meshing of the second end-side toothing in the external toothing of the inner ring, so that reference is made to the above description in principle. In particular, with surface contact or surface pressing between the second end-side toothing of the respective piston and the external toothing of the inner ring, particularly high torques can be transmitted between the crankshaft and the inner ring or, if applicable, the guide unit - in comparison with solutions with linear contact.

[0060] Furthermore, a plurality of teeth, in particular three teeth, can be provided in each case in the toothing on the second end face in order to transmit particularly high torques between the crankshaft and the inner ring or, if appropriate, the guide unit.

[0061] When the guide unit is braked or fixed, one or each piston drives the hollow shaft and the inner ring alternately. Both the inner ring and the hollow shaft can be used as the driven part. It is also possible to use only the hollow shaft or the inner ring as the driven part, wherein the other element is braked or locked.

[0062] Since the inner ring has a smaller diameter than the hollow shaft, a lower tangential speed can be achieved or obtained at the inner ring at the same angular speed. In other words, two driven parts for different speeds can be provided at the same time through the inner ring and the hollow shaft. As a result, a possible second transmission mechanism can be saved depending on the application.

[0063] The inner ring can, but need not necessarily, be connected to the hollow shaft in a rotationally fixed manner, wherein, in the case of a connection, on the one hand, a higher resolution of the coaxial transmission can be achieved. On the other hand, it is possible to transmit higher torques.

[0064] Furthermore, theoretically, an embodiment variant with only two pistons is also conceivable, in which, due to the meshing of a total of four (pistons), it is ensured by means of the inner ring that the hollow shaft or, if applicable, the guide unit moves further only in a certain direction.

[0065] Finally, it is also possible for the inner ring to rotate in a direction opposite to the direction of rotation of the hollow shaft.

[0066] In a preferred embodiment of the coaxial transmission according to the invention, it is provided that the guide unit is arranged immovably relative to the axis of rotation. In this case, the hollow shaft is allowed to continue to move and serves as a driven element. If necessary, in this embodiment variant, the inner ring (if present) can also continue to rotate, the inner ring can be braked again or can be used as a driven element.

[0067] As already mentioned above, by means of arranging a plurality of star-shaped connecting rods one behind the other on different crank pins as viewed along the axis of rotation, other, more precisely very high, transmission ratios can be achieved in a simple manner. Accordingly, in a preferred embodiment of the coaxial transmission according to the invention, it is provided that the rotational movement of the hollow shaft about the axis of rotation is locked or braked, another crank pin is provided, another piston group having a plurality of pistons is provided, the pistons of the other piston group each having a toothing with at least one tooth on a first end side facing away from the axis of rotation, another connecting rod constructed in a star shape is provided in order to connect the pistons of the other piston group with the other crank pin, the pistons of the other piston group are coupled to the other connecting rod constructed in a star shape, and another hollow shaft with an internal toothing is provided, wherein, as viewed in a plane perpendicular to the axis of rotation, at least the The internal tooth portion of the other hollow shaft, preferably the entire other hollow shaft, is arranged within the cross section of the hollow shaft, and the pistons of the other piston group are respectively linearly guided in the guide unit and can reciprocate parallel to the radial direction, whereby, when the guide unit rotates around the rotation axis, the tooth portion on the first end side of the piston of the other piston group can be placed in a state of meshing with the internal tooth portion of the other hollow shaft and a state of disengagement from the internal tooth portion of the other hollow shaft in sequence, so that during the corresponding meshing period, preferably with surface contact between the corresponding tooth portion and the internal tooth portion of the other hollow shaft, the other hollow shaft continues to rotate around the rotation axis.

[0068] In this embodiment, the guide unit is not arranged immovably relative to the axis of rotation, but rather is locked or braked, whereas the hollow shaft is locked.

[0069] The output is realized on a further hollow shaft.

[0070] In this case, the guide unit guides both the pistons of the at least one piston group and also the pistons of the other piston group.

[0071] Observe along the axis of rotation, at least one crank pin and another crank pin or another eccentric are arranged in succession, wherein at least one crank pin and another crank pin do not necessarily have to be arranged to be directly connected to each other or directly connected to each other. That is to say, intervals can also be set between the crank pins.

[0072] It is of course possible to provide a plurality of further crank pins, a plurality of further piston groups, a plurality of further connecting rods designed in a star shape, and also a plurality of further hollow shafts, wherein these are usually arranged one behind the other as viewed along the axis of rotation.

[0073] In the resulting two-stage or multi-stage embodiment of the coaxial transmission, on the one hand a relatively large number of teeth are involved in the power transmission, whereby higher torques can be transmitted. On the other hand, relatively high transmission ratios, in particular reduction transmission ratios, can be achieved.

[0074] In this case, the transmission ratio i is calculated from the number of teeth zf of the fixed or braked stage (that is, the number of teeth of the internal toothing of the hollow shaft) and the number of teeth za of the driven stage (that is, the number of teeth of the internal toothing of the further hollow shaft) according to i=za*(zf-1) / (za-zf). For example, if the internal toothing of the hollow shaft has 42 teeth and the internal toothing of the further hollow shaft has 41 teeth, then the total transmission ratio i=-1681 is obtained, i.e. a very high reduction ratio (also colloquially referred to as reduction ratio), since |i|>>1. The negative sign indicates that the guide unit and the further hollow shaft rotate in opposite directions.

[0075] Accordingly, in order to achieve a high transmission ratio bandwidth and in particular a high transmission ratio, in a particularly preferred embodiment of the coaxial transmission according to the invention it is provided that the internal toothing of the hollow shaft and the internal toothing of the further hollow shaft have different numbers of teeth.

[0076] In principle, the eccentricity of the at least one crank pin and the further crank pin can be different in size. In a particularly preferred embodiment of the coaxial transmission according to the invention, it is provided that the at least one crank pin and the further crank pin have the same eccentricity. This has proven to be advantageous in terms of good mass balance.

[0077] A certain crankpin offset that is not zero has also proven to be advantageous with regard to good mass balance. Therefore, in a particularly preferred embodiment of the coaxial transmission according to the invention, it is provided that the at least one crankpin and the further crankpin are arranged offset relative to one another with respect to the axis of rotation, preferably by 360° / h, wherein h is the total number of all crankpins.

[0078] In terms of mass balance, a crankpin offset of 360° / h has proven to be optimal, where h is the sum of the number of the at least one crankpin and the further crankpins. That is, if, in the described embodiment of the coaxial transmission, for example, exactly one crankpin and exactly one further crankpin are provided, h=2 results in a crankpin offset of 360° / 2=180° between the crankpin and the further crankpin. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Now, the invention is explained in detail based on embodiments. The drawings are exemplary and, although they are intended to clarify the idea of ​​the invention, they are by no means intended to reflect the idea of ​​the invention in a narrowing or even exclusive manner.

[0080] in:

[0081] Figure 1 A schematic cross-sectional view showing a first embodiment of a coaxial transmission according to the present invention is shown,

[0082] Figure 2 A schematic cross-sectional view showing a second embodiment of a coaxial transmission according to the present invention is shown,

[0083] Figure 3 A schematic sectional view of a second exemplary embodiment of a coaxial transmission according to the invention is shown, in which the guide section can be seen.

[0084] Figure 4 A schematic cross-sectional view or end view of a third embodiment of a coaxial transmission according to the invention is shown,

[0085] Figure 5 Shown along the Figure 4 Schematic cross-sectional view of a third embodiment of the invention along the section line VV in FIG. 1 , wherein the arrow indicates the viewing direction,

[0086] Figure 6 Shown along the Figure 5 Schematic sectional view of a third exemplary embodiment along the section line VI-VI in FIG. 1 , wherein the arrows indicate the viewing direction. DETAILED DESCRIPTION

[0087] exist Figure 1 A first embodiment of a coaxial transmission 1 according to the invention is shown in a cross-sectional view of FIG. The coaxial transmission 1 has a crankshaft 3 which is rotatable about an axis of rotation 2 and has a crank pin 4 which is located at Figure 1 An eccentric wheel can be seen in FIG. 2 and forms the eccentric wheel which rotates when the crankshaft 3 rotates about the rotation axis 2 .

[0088] The coaxial transmission 1 of the first exemplary embodiment also has a piston group with nine pistons 5 a - i. Each of the pistons 5 a - i has a stamped toothing 11 with teeth on a first end face 10 facing away from the axis of rotation 2 .

[0089] Furthermore, a hollow shaft 7 is provided in the coaxial transmission 1, which has an internal toothing 8. Figure 1 In the plane of the drawing, the pistons 5a-i and the crankshaft 3 are arranged at least partially in the hollow shaft 7. This also applies to the guide unit 9, in which the pistons 5a-i are each linearly guided and can reciprocate parallel to the radial direction 12 perpendicular to the rotation axis 2. For this purpose, the guide unit 9 has a hollow cylinder in the embodiment shown, which serves as a linear guide for the pistons 5a-i. The pistons 5a-i have a circular cross section in the section arranged in the hollow cylinder of the guide unit 9, wherein the corresponding cross section is located in a plane perpendicular to the corresponding radial direction 12.

[0090] By the reciprocating movement of the pistons 5a-i, the toothing 11 of the first end side 10 of the pistons 5a-i is successively brought into a state of meshing with the internal toothing 8 and into a state of disengagement from the internal toothing 8, wherein, due to the linear movement of the pistons 5a-i, a surface contact between the corresponding toothing 11 and the internal toothing 8 can be ensured during the corresponding meshing, and the corresponding toothing is pressed against the internal toothing 8 in a surface manner. As a result, the hollow shaft 7 is rotated a little further about the rotation axis 2 when the guide unit 9 is arranged so as to be immovable relative to the rotation axis 2 or when the guide unit 9 is arranged so as to be rotatable about the rotation axis 2 but is braked. Conversely, if the hollow shaft 7 is fixed, to be precise immovable relative to the rotation axis 2 or is braked, the guide unit 9 (which is mounted so as to be rotatable about the rotation axis 2) is rotated a little further. Due to the surface engagement or pressing, very high torques can be transmitted from the crankshaft 3 to the hollow shaft 7 or, if necessary, to the guide unit 9.

[0091] Preferably, Figure 1-3 In the exemplary embodiment shown in FIG. 2 , the guide unit is arranged immovably relative to the axis of rotation 2 , so that the hollow shaft 7 is moved when the crankshaft 3 rotates.

[0092] According to the invention, a common, star-shaped connecting rod 6 is provided to connect the pistons 5a-i of the piston group to the crank pin 4, with which the pistons 5a-i are coupled. This results in a substantially non-offset arrangement of the pistons 5a-i relative to the axis of rotation 2 in the illustrated embodiment, which results in a very small overall length of the coaxial transmission 1 measured parallel to the axis of rotation 2, despite the relatively high rotational speeds of the pistons 5a-i. At the same time, due to the relatively large number of pistons 5a-i, a very uniform introduction of force is achieved, and in addition, very high torques can be transmitted.

[0093] In order to ensure the orbital movement and prevent the otherwise star-shaped connecting rod 6 from rotating relative to the guide unit 9, Figure 1-3 In the embodiment shown in FIG. 2 , two guide pins 16 are provided, which are rigidly connected to the star-shaped connecting rod 6 and extend from the connecting rod in a manner extending parallel to the rotation axis 2. The guide pins 16, in particular the sections of the guide pins 16 with the free ends, engage with corresponding recesses 17 of the guide section 19, or are arranged partially in the recesses 17, see FIG. Figure 3 , wherein the guide section 19 is arranged immovably relative to the guide unit 9 , or is connected to the guide unit. In the exemplary embodiment shown, the corresponding recess 17 is designed as a hole, wherein the size of the recess 17 is matched to the eccentricity of the crank pin 4 .

[0094] The coupling between the pistons 5a-i and the star-shaped connecting rod 6 can be realized in different ways. Figure 1 In the first embodiment shown in FIG. 1 , in order to couple the pistons 5a-i of the piston group with the associated connecting rod 6 configured in a star shape, an elongated hole 13 extending transversely to the corresponding radial direction 12 is provided in the piston 5a-i, wherein a coupling pin 14 is fastened to the connecting rod 6 configured in a star shape, the coupling pin engaging with the elongated hole 13, or rather being partially arranged in the elongated hole 13. That is, the movement of the piston 5a-i is thereby realized according to the principle of a crank slider. In the embodiment shown, the elongated hole 13 extends substantially straight and substantially perpendicular to the corresponding radial direction 12 and substantially perpendicular to the axis of rotation 2. The coupling pin 14 again extends substantially parallel to the axis of rotation 2, or rather extends parallel to the axis of rotation 2 from the connecting rod 6 configured in a star shape.

[0095] In accordance with Figure 1 In the first embodiment, two of the coupling pins 14 form guide pins 16 in that they are slightly longer than the remaining coupling pins 14 and extend through the corresponding elongated holes 13 into the corresponding recesses 17 of the guide section 19. This further reduces the number of parts.

[0096] exist Figure 2 The second embodiment shown in the figure differs from the first embodiment only in the coupling of the pistons 5a-i to the connecting rod 6 configured in a star shape, and therefore, the basic working principle of the coaxial transmission device 1 refers to the above description. Specifically, in the second embodiment, it is provided that in order to couple the pistons 5a-i of the piston group with the connecting rod 6 configured in a star shape, a substantially rigid intermediate element 15 is provided, wherein each intermediate element 15 is articulatedly connected to the associated piston 5a-i on the one hand, and is articulatedly connected to the connecting rod 6 configured in a star shape on the other hand.

[0097] In the embodiment shown, connecting bolts 18 are provided for the articulated connection between the respective intermediate element 15 and the star-shaped connecting rod 6, which define the swivel joint or its axis of rotation, wherein the axis of rotation is parallel to the axis of rotation 2. In this case, the connecting bolts 18 extend from the star-shaped connecting rod 6 parallel to the axis of rotation 2. In order to save parts, two of the connecting bolts 18 also form guide pins 16 in that they are slightly longer than the remaining connecting bolts 18 and extend into corresponding recesses 17 of the guide section 19, see Figure 3 .

[0098] In the second exemplary embodiment shown, the articulated connection between the respective intermediate element 15 and the associated piston 5 a - i is respectively realized by means of a swivel joint 20 , wherein the axis of rotation of the swivel joint 20 extends parallel to the axis of rotation 2 .

[0099] exist Figure 1 and Figure 2 In both exemplary embodiments shown, the crankshaft 3 is each designed to be hollow along the axis of rotation 2 , which allows, for example, a torsion-free passage of cables (not shown).

[0100] Unless otherwise specified, the above description is applicable to the third embodiment, and the corresponding repetition is omitted. Figure 4 , Figure 5 and Figure 6 In the third embodiment shown in FIG. 1 , the guide unit 9 is not arranged immovably or locked or braked with respect to the rotational movement about the rotational axis 2 , but rather the hollow shaft 7 is locked or braked.

[0101] In this case, the coaxial transmission 1 comprises a further crank pin 21 and a further piston group with a plurality of pistons 23 a - t , each of which has a toothing 11 with at least one tooth on a first end face 10 facing away from the axis of rotation 2 .

[0102] In this embodiment, the eccentric shaft or crankshaft 3 is manufactured in one piece with the eccentric wheel or crank pin 4 and a further eccentric wheel or a further crank pin 21, wherein the crank pins 4, 21 are arranged directly adjacent to each other as viewed along the axis of rotation 2, see Figure 5 .

[0103] In order to connect the pistons 23 a - t of the other piston group to the other crank pin 21 , a further connecting rod 22 of star-shaped design is provided, to which the pistons 23 a - t of the other piston group are coupled.

[0104] In order to couple the piston 23a-t with the star-shaped further connecting rod 22, an intermediate element 15 is provided again, in this case, not an intermediate element of the star-shaped connecting rod 6, but an intermediate element of the star-shaped further connecting rod 22. The intermediate element 15 is rotatably supported on the side of the star-shaped further connecting rod 22 by means of a connecting bolt 18, and is rotatably supported on the side of the piston 23a-t by means of a swivel joint 20, wherein the associated rotation axis extends parallel to the rotation axis 2.

[0105] The other star-shaped connecting rod 22 is supported on the other crank pin 21 by means of a bearing—similar to the bearing of the star-shaped connecting rod 6 on the crank pin 4 —which is formed by a needle bearing 26 in the exemplary embodiment shown.

[0106] In the third exemplary embodiment shown, the coaxial transmission 1 further comprises a further hollow shaft 24 with an internal toothing 25, wherein the entire further hollow shaft 24 is arranged in the cross section of the hollow shaft 7, in particular with reference to Figure 4 and Figure 5 .

[0107] In the third embodiment shown, the hollow shaft 7 and the further hollow shaft 24 are arranged one after the other along the axis of rotation 2 in such a way that the further hollow shaft 24 is located outside the hollow shaft 7 and is directly connected to the hollow shaft. However, it is of course also possible for the hollow shaft 7 to extend beyond the further hollow shaft 24 parallel to the axis of rotation 2, in particular by a section 27 of the hollow shaft 7 without the internal toothing 8. Alternatively, the section 27 of the hollow shaft 7 without the internal toothing can form a bearing, in particular a sliding bearing, for the further hollow shaft 24. Figure 5 In FIG. 8 , such a possible geometry or design of the hollow shaft 7 with a section 27 without internal toothing is indicated by dotted lines.

[0108] The pistons 23a-t of the other piston group are linearly guided in the guide unit 9, just like the pistons 5a-t of the piston group, and can reciprocate parallel to the radial direction 12. As a result, when the guide unit 9 rotates about the rotation axis 2, the toothing 11 of the first end side 10 of the piston 23a-t of the other piston group is successively placed in a state of meshing with the internal toothing 25 of the other hollow shaft 24 and a state of disengagement from the internal toothing 25 of the other hollow shaft 24, so that the other hollow shaft 24 is further rotated about the rotation axis 2 during the corresponding meshing, preferably with surface contact between the corresponding toothing 11 and the internal toothing 25 of the other hollow shaft 24.

[0109] In this way, a two-stage coaxial transmission 1 is realized, wherein the further hollow shaft 24 is used as the output part and a particularly high transmission ratio can be achieved. In this regard, in the third embodiment shown, the inner toothing 8 of the hollow shaft 7 and the inner toothing 25 of the further hollow shaft 24 have different numbers of teeth.

[0110] Specifically, in the third embodiment shown, the number of teeth za of the inner toothing 25 of the other hollow shaft 24 is za=41, and the number of teeth zf of the inner toothing 8 of the hollow shaft 7 is zf=42. As a result, as the total transmission ratio, i=za*(zf-1) / (za-zf)=-1681 is obtained, that is, a very high reduction transmission ratio, wherein the guide unit 9 and the other hollow shaft 24 rotate in opposite directions.

[0111] In the third embodiment shown, the crank pin 4 and the further crank pin 21 have the same eccentricity, see Figure 5 , which has a positive effect on the mass balance.

[0112] Furthermore, in the third embodiment shown, a crank pin offset of 180° is provided in order to optimize the mass balance. That is, the crank pin 4 and the further crank pin 21 are arranged offset by 180° relative to the rotation axis 2, see Figure 5 .

[0113] List of Reference Numerals

[0114] 1Coaxial transmission device

[0115] 2Rotation axis

[0116] 3 Crankshaft

[0117] 4 Crank pin

[0118] 5a-i, jt piston

[0119] 6 Connecting rods constructed in a star shape

[0120] 7Hollow shaft

[0121] 8Inner teeth of hollow shaft

[0122] 9 Guidance Unit

[0123] 10 First end side of piston

[0124] 11 Toothed portion on the first end side

[0125] 12 Radial

[0126] 13 Long hole

[0127] 14 coupling pin

[0128] 15 Intermediate components

[0129] 16 guide pins

[0130] 17 Notch

[0131] 18 Connecting bolt

[0132] 19 Boot Segment

[0133] 20 Rotary joints

[0134] 21 additional crank pin

[0135] 22 Another connecting rod constructed in a star shape

[0136] 23a-t Piston of another piston group

[0137] 24 Another hollow shaft

[0138] 25 The inner tooth portion of the other hollow shaft

[0139] 26 Needle roller bearings

[0140] 27 The section of the hollow shaft without internal teeth

Claims

1. A coaxial transmission device (1), comprising a crankshaft (3) rotatable about an axis of rotation (2) and having at least one crank pin (4), the coaxial transmission device (1) further comprising at least one piston group, the at least one piston group comprising a plurality of pistons (5a-i), each of the pistons having a toothing (11) with at least one tooth on a first end side (10) remote from the axis of rotation (2), the coaxial transmission device (1) further comprising a hollow shaft (7) having an internal toothing (8), wherein: The pistons (5a-i) are arranged inside the hollow shaft (7) when viewed in a plane perpendicular to the axis of rotation (2). The coaxial transmission (1) also includes a guide unit (9), wherein the pistons (5a-i) are respectively linearly guided in the guide unit (9) and can reciprocate parallel to a radial direction (12) perpendicular to the rotation axis (2), whereby the toothing (11) of the first end side (10) of the piston (5a-i) can be placed in a state of meshing with the internal toothing (8) and disengaging from the internal toothing (8) in sequence, so that the hollow shaft (7) or the guide unit (9) continues to rotate around the rotation axis (2) during the corresponding meshing period, characterized in that in order to connect the pistons (5a-i) of the corresponding piston group with the at least one crank pin (4), a common, star-shaped connecting rod (6) is respectively provided, and the pistons (5a-i) of the corresponding piston group are coupled to the connecting rod.

2. The coaxial transmission device (1) according to claim 1, characterized in that: A plurality of piston groups are provided, wherein a common, star-shaped connecting rod (6) is provided for each piston group, to which the pistons (5a-i) of the respective piston group are coupled.

3. The coaxial transmission device (1) according to any one of claims 1 to 2, characterized in that: In order to ensure the orbital movement and prevent any further rotation of the corresponding star-shaped connecting rod (6) relative to the guide unit (9), at least two guide pins (16) are provided, which are rigidly connected to the corresponding star-shaped connecting rod (6) and engage with at least one corresponding recess (17) of at least one guide section (19) arranged so as to be immovable relative to the guide unit (9).

4. The coaxial transmission device (1) according to claim 3, characterized in that: A roller is arranged on the guide pin (16) for facilitating the guide pin (16) to roll on the at least one guide section (19) when the guide pin (16) moves in at least one corresponding recess (17).

5. The coaxial transmission device (1) according to claim 1 or 2, characterized in that: In order to couple the pistons (5a-i) of the corresponding piston group with the associated star-shaped connecting rod (6), a long hole (13) extending transversely to the corresponding radial direction (12) is provided in the piston (5a-i), wherein a coupling pin (14) engaging with the long hole (13) is fastened to the star-shaped connecting rod (6).

6. The coaxial transmission device (1) according to claim 5, characterized in that: In order to ensure the orbital movement and prevent any further rotation of the corresponding, star-shaped connecting rod (6) relative to the guide unit (9), at least two guide pins (16) are provided, which are rigidly connected to the corresponding star-shaped connecting rod (6) and engage with at least one corresponding recess (17) of at least one guide section (19) arranged so as to be immovable relative to the guide unit (9), at least one of the coupling pins (14) also forming at least one guide pin (16).

7. The coaxial transmission device (1) according to claim 1 or 2, characterized in that: In order to couple the pistons (5a-i) of the corresponding piston group with the associated star-shaped connecting rod (6), an intermediate element (15) of essentially rigid design is provided, wherein each intermediate element (15) is articulated on the one hand with the associated piston (5a-i) and on the other hand with the star-shaped connecting rod (6).

8. The coaxial transmission device (1) according to claim 7, characterized in that: In order to ensure the orbital movement and prevent any further rotation of the corresponding star-shaped connecting rod (6) relative to the guide unit (9), at least two guide pins (16) are provided, which are rigidly connected to the corresponding star-shaped connecting rod (6) and engage with at least one corresponding recess (17) of at least one guide section (19) which is arranged so as to be immovable relative to the guide unit (9), and in order to form an articulated connection between the corresponding intermediate element (15) and the associated star-shaped connecting rod (6), connecting bolts (18) are provided, wherein at least one of the connecting bolts (18) also forms a guide pin (16).

9. The coaxial transmission device (1) according to claim 1 or 2, characterized in that: The toothing (11) of the first end side (10) comprises a plurality of teeth.

10. The coaxial transmission device (1) according to claim 1 or 2, characterized in that: The crankshaft (3) is designed to be hollow.

11. The coaxial transmission device (1) according to claim 1 or 2, characterized in that: The pistons (5a-i) each have a toothing with at least one tooth on a second end side opposite to the first end side (10), and an inner ring with an external toothing which is supported so as to be rotatable about an axis of rotation (2), wherein a guide unit (9) is at least partially arranged between the inner ring and the hollow shaft (7), wherein the toothing on the second end side of the pistons (5a-i) can be placed in a state of meshing with the external toothing and disengaging from the external toothing in sequence, so that during the corresponding meshing period, the inner ring or the guide unit (9) continues to rotate about the axis of rotation (2).

12. The coaxial transmission device (1) according to claim 1 or 2, characterized in that: The guide unit (9) is arranged so as to be immovable with respect to the rotation axis (2).

13. The coaxial transmission device (1) according to claim 1 or 2, characterized in that: Locking or braking the rotational movement of the hollow shaft (7) about the rotation axis (2), A further crank pin (21) is provided, a further piston group having a plurality of pistons (23a-t) is provided, the pistons of the further piston group each having a toothing (11) with at least one tooth on a first end side (10) remote from the axis of rotation (2), In order to connect the pistons (23a-t) of the other piston group to the other crank pin (21), a further connecting rod (22) configured in a star shape is provided, to which the pistons (23a-t) of the other piston group are coupled. A further hollow shaft (24) having an internal toothing (25) is provided, wherein, viewed in a plane perpendicular to the axis of rotation (2), at least the internal toothing (25) of the further hollow shaft (24) is arranged within the cross section of the hollow shaft (7), The pistons (23a-t) of the other piston group are respectively linearly guided in the guide unit (9) and can reciprocate parallel to the radial direction (12), so that when the guide unit (9) rotates around the rotation axis (2), the toothed portion (11) of the first end side (10) of the piston (23a-t) of the other piston group can be placed in a state of meshing with the internal toothed portion (25) of the other hollow shaft (24) and disengaging from the internal toothed portion (25) of the other hollow shaft (24) in sequence, so that during the corresponding meshing period, the other hollow shaft (24) can continue to rotate around the rotation axis (2).

14. The coaxial transmission device (1) according to claim 13, characterized in that The inner toothing (8) of the hollow shaft (7) and the inner toothing (25) of the further hollow shaft (24) have different numbers of teeth.

15. The coaxial transmission device (1) according to claim 13, characterized in that: The at least one crank pin (4) and the further crank pin (21) have the same eccentricity.

16. The coaxial transmission device (1) according to claim 13, characterized in that: The at least one crank pin (4) and the further crank pin (21) are arranged offset relative to each other with reference to the rotation axis (2).

17. The coaxial transmission device (1) according to claim 1, characterized in that: The at least one piston group has at least three pistons (5a-i).

18. The coaxial transmission device (1) according to claim 1, characterized in that: The toothing (11) of the first end side (10) of the piston (5a-i) can be placed in a state of meshing with the internal toothing (8) and disengaging from the internal toothing (8) in sequence, so that during the corresponding meshing period, with surface contact between the corresponding toothing (11) and the internal toothing (8), the hollow shaft (7) or the guide unit (9) can continue to rotate around the rotation axis (2).

19. The coaxial transmission device (1) according to claim 9, characterized in that: The toothing (11) of the first end side (10) comprises three teeth in each case.

20. The coaxial transmission device (1) according to claim 11, characterized in that: The toothing on the second end side of the piston (5a-i) can be placed in a state of engagement with the external toothing and disengagement with the external toothing in sequence, so that during the corresponding engagement period, the inner ring or guide unit (9) continues to rotate around the rotation axis (2) with surface contact between the corresponding toothing and the external toothing.

21. The coaxial transmission device (1) according to claim 13, characterized in that: The entire further hollow shaft (24) is arranged within the cross section of the hollow shaft (7).

22. The coaxial transmission device (1) according to claim 13, characterized in that When the guide unit (9) rotates about the rotation axis (2), the toothing (11) of the first end side (10) of the piston (23a-t) of the other piston group can be placed in a state of meshing with the internal toothing (25) of the other hollow shaft (24) and disengaging from the internal toothing (25) of the other hollow shaft (24) in sequence, so that during the corresponding meshing, the other hollow shaft (24) can continue to rotate about the rotation axis (2) with surface contact between the corresponding toothing (11) and the internal toothing (25) of the other hollow shaft (24).

23. The coaxial transmission device (1) according to claim 16, characterized in that The at least one crank pin (4) and the further crank pin (21) are arranged offset relative to one another by 360° / h with respect to the axis of rotation (2), wherein h is the total number of all crank pins.

Images