ELASTIC CAM COUPLING WITH REDUCED BENDING TORQUES

Description

[0001] The invention relates to a cam clutch, in particular a package cam clutch for systems, machines and vehicles for transmitting particularly high torques.

[0002] The invention particularly relates to an elastic cam coupling with numerous pairs or packages of interconnected cams and mechanical, pneumatic or hydraulic spring elements, wherein the innovative technical design of the coupling results in only low bending moments on the cams under load.

[0003] A multi-layer clutch is used to transmit high torques in the torsional direction while simultaneously providing low restoring forces in the axial, radial, and cardanic directions. The hydraulic design has particularly low restoring forces in the radial direction. This is achieved using state-of-the-art technology, where a drive disk with cams and a driven disk with cams are connected by rubber elements.

[0004] WO 2011 / 088965 discloses a package coupling consisting of a star-shaped drive disk with straight, non-angled cams and a star-shaped driven disk with offset or recessed cams that are open to the outside, allowing better access to the preload screws required for preloading. The drive and driven disks are connected to each other via the cams by special, mechanically adjustable elastomer springs of equal size with respect to their contact surface ( Fig. 1 ).

[0005] WO 2011 / 088860 A1 and WO 2013 / 041082 A1 disclose package couplings which are formed from two opposing, star-shaped, mutually offset coupling parts. A cam element equipped with fastening means is attached to the free end of each arm of the two star-shaped coupling parts, with a flush, vulcanized elastic spring element. While the cam elements of one coupling part are arranged straight, or as an extension of the star-shaped arms, and thus without any lateral angular offset, the cam elements of the other coupling part are arranged substantially laterally offset, in such a way that, when the two coupling parts are joined together, an undivided elastic coupling ring is formed which can generate a uniform tangential preload ( Fig. 2 ). The two patent applications mentioned differ in the design of the cams and the elastic spring elements and have different objectives: to provide a coupling with simplified assembly (WO 2013 / 041082 A1) or a coupling with greater compactness and lower weight (WO 2011 / 088860 A1).

[0006] The patent specification GB 238,064 describes a shaft coupling with annular or U-shaped elastic elements attached to a three-armed running hub with cam elements.

[0007] In the aforementioned prior art clutches, as described, the cams of the drive disk and the driven disk enclose the rubber or spring elements. The cams of both disks must be at least as long as the width or diameter of the elastic elements. This in turn means that the clutch disks of the known clutches must be relatively far apart. Due to the drive torque, undesirable transverse bending moments arise, particularly in the cam elements arranged laterally offset from the respective disk. These must therefore have a relatively thick material to transmit the not inconsiderable local bending moments. Furthermore, these parts of the clutch are more easily subject to material fatigue. Increasing the material thickness not only requires more space but also significantly increases the weight.Couplings intended for large systems or machines with high torques often reach a weight of several tons, so weight savings through a lighter and more effective design of the coupling is very desirable.

[0008] The task was therefore to provide a coupling for the transmission of particularly high torques, for example > 5,000 kNm, which has a narrow and weight-reduced design and generates only low bending forces in the coupling under load, especially in the area of ​​the cams.

[0009] The object has been achieved by providing a cam clutch as set out and specified below and in the claims.

[0010] The invention thus relates to an elastic package cam clutch, comprising a drive disk (1) with a base body and with support cams (7) projecting outwards therefrom in a star shape, and a substantially equally sized driven disk (2) with a base body and with support cams (8) projecting outwards therefrom in a star shape, wherein the disks (1)(2) are arranged opposite one another and axially offset from one another and have elements or devices for transmitting a torque of a drive shaft of the first machine part to an output shaft of the second machine part, and the support cams (7) of the drive disk (1) are connected to the support cams (8) of the output disk (2) via elastic spring elements (3), wherein both the support cams (7 of the

[0011] The drive pulley (1) and the support cams (8) of the driven pulley (2) have a preferably identical angle of attack (14) relative to the plane of the two opposing pulleys (1)(2), which angle is directed such that they are arranged at an angle to one another. According to the invention, the elastic spring elements (3) are dimensioned such that they project beyond the support cams (7)(8) adjacent on both sides by means of preferably cylindrically or conically shaped components that function as projections (23) or projecting adapter discs.

[0012] The size of the respective projecting adapter disc, which can be an independent component, an integral part of the elastic spring elements (3), or an integral part of the support cams (7)(8), is defined according to the invention by the ratio of the diameter (21) of the elastic projecting, preferably round or oval spring elements (3) to the thickness (22) of the support or the cam side surfaces of the adjacent narrower support cams (7)(8), and according to the invention takes values ​​between 1.2 and 2.0, preferably between 1.4 and 1.8.

[0013] According to the invention, the said angle of attack (14) of the support cams (7)(8) inclined towards one another is not more than 30°, in particular 10 - 30°, preferably not more than 20°, in particular 15 - 20°.

[0014] According to the invention, the drive and driven pulleys (1)(2) or their base bodies each have 3-12, preferably 4-10, in particular 6-8 support cams (7)(8), which are connected to each other by twice the number of elastic spring elements (3). In principle, however, the base bodies can also have more than 12 support cams arranged in a star shape.

[0015] The coupling according to the invention has a significantly slimmer design than comparable conventional couplings (see Fig. 4 ). This slimmer design has the advantage that the carrier cams (7)(8) can be interlaced so tightly in a small space that the distance (9) between the drive pulley (7) and the driven pulley (8) can be small without a collision of the individual cams in the crossing areas (20) of the carrier cams occurring during operation.

[0016] In such a coupling, when subjected to high torques, only relatively small bending moments (6) are generated in the area of ​​the cam axes (17) of the coupling ring in comparison to the known couplings of the prior art: Due to the smaller projection of the support cams (7)(8), the bending moment (6) acting around an imaginary cam axis (17) aligned radially and perpendicular to the coupling rotation axis (18) is reduced, whereby the bending loads in the individual support cams are significantly smaller and thus the loads can be transmitted despite the smaller cross sections (22).

[0017] The resulting weight reduction of the coupling according to the invention is a factor of 1.5 to 2 compared to a conventional coupling. For a coupling weight of, for example, six tonnes, the design according to the invention can save 2 - 3 tonnes of weight, which is ultimately a significant material and therefore cost factor.

[0018] The elastic spring elements (3) of the coupling according to the invention can be known layered spring elements made of one or more elastic layers which are separated from one another by inelastic support plates.

[0019] Such layered springs can be mechanically adapted in their stiffness, as described, for example, in WO 2011 / 088965 A1.

[0020] To allow the clutch a degree of radial freedom, elastomer hydraulic elements are preferably used as spring elements (3) according to the invention. For example, the hydraulic elastomer elements described in EP 2 003 362 B1 or EP 1 566 543 B1 can be used very effectively.

[0021] According to the invention, these elements are hydraulically interconnected via appropriate lines to enable radial displacement through fluid exchange. For this purpose, the fluid chambers of all pressure-side elements and the fluid chambers of all relief-side elements are hydraulically connected to each other. Thus, the coupling according to the invention exhibits low rigidity not only in the axial and cardanic directions, but also in the radial direction, so that it essentially only transmits rotational forces.

[0022] In a further embodiment of the invention, the torque of the clutch according to the invention can be temporarily limited, if desired. For this purpose, a pressure diaphragm bladder accumulator is added to the pressure-side hydraulic circuit. This is filled with the maximum pressure occurring during normal operation. At higher pressures due to extreme load peaks, hydraulic fluid is forced into the diaphragm bladder accumulator, allowing for greater spring travel in the event of an overload. As soon as the force drops back to a normal level, the diaphragm bladder accumulator forces the hydraulic fluid out again, and the system continues to operate normally.

[0023] The invention therefore also relates to a corresponding elastic cam clutch which, as elastic spring elements (3), not only has static or mechanically adjustable layered spring elements or pneumatic spring elements but instead hydraulic spring elements or hydraulic elastomer elements or a combination of these, wherein the hydraulics are preferably arranged and operated in such a way that the elastic spring elements (3) also have a low rigidity in the radial direction, so that the clutch can essentially only transmit rotational forces.

[0024] The advantageous properties of the coupling according to the invention can be summarized as follows: Low bending load in the cam area of ​​the coupling by means of support cams which are inclined on both sides and which cross but do not collide, each with an angle of attack of < 30°, preferably < 20°, and cam thicknesses which are significantly smaller than the projecting adjacent elastic spring elements, wherein in one embodiment of the invention the different diameters are achieved by means of conical or cylindrical adapter discs which are cast / forged or directly attached to the elastomer part; this results in a narrow, space-saving and low-weight and therefore material-saving and cost-effective design; identical or similar adapter discs can be used.identical disks are used for the drive disk and driven disk; by using elastic, preferably adjustable hydraulic elements, optionally with pressure limitation through the use of pressure diaphragm bladder accumulators, the coupling according to the invention can be adjusted so that it essentially only transmits rotational forces; universal use in general plant, machine and vehicle construction for the low-constraint transmission of, in particular, larger torques; the coupling is preferably intended, but not limited to, use in wind turbines, in particular in the drive train of wind turbines with correspondingly large torques of more than 5000 kNm; in this case preferably between the rotor bearing and the gearbox or between the rotor bearing and the generator; .

[0025] The figures are described in more detail below: Fig. 1 : shows a prior art coupling as disclosed in WO 2011 / 088965 A1. This embodiment is described in more detail earlier in this application. Fig. 2 :shows the sketch of the concept of the clutches as described in WO 2011 / 088860 A1 and WO 2013 / 041082 A1 using clutches with a different design. Details are also set out earlier in this application. While the front clutch disc has star-shaped, straight and non-offset cams (7'), the rear clutch disc is provided with laterally offset cams (8') which are arranged such that they fit into the spaces between the cams (7') of the front disc and are connected to them via spring elements (3'). This results in a considerable bending moment (6') in the area of ​​these cams offset laterally to the disc and thus necessarily also a greater distance between the two clutch discs. This in turn requires a larger bending lever (5) between the force line of action and the force introduction into the respective spring element. Fig. 3 :shows various views of a cam clutch according to the invention. (A) shows a plan view of the clutch according to the invention. This comprises two identical base bodies, each consisting of 10 star-shaped support cams (7) (front disc (1)) and 10 star-shaped support cams (8) (rear disc (2)). The support cams of the rear disc are located in the spaces between the front discs and, together with these and the elastic spring elements (3) arranged between them, form the actual clutch ring. The torque force line essential to the invention is designated by (4). (B) shows a perspective view of the clutch according to the invention. It can be seen that both clutch discs (1) and (2) with their support cams (7) and (8) are axially angularly offset. The support cams (7) and (8) are inclined towards one another and have an identical angle of attack.This allows the base bodies of the clutch discs to be positioned very close together without the cams touching each other in their intersection areas (20) during operation. It can also be seen that the round spring elements (3) here protrude beyond the cam end areas, i.e. they have a larger diameter than the thickness / width of the adjacent cams. (C) shows on the left-hand side the clutch according to the invention according to Fig. 1 (A) and (B) from a side view. The right-hand side shows an enlarged section. Position (6) represents the bending moment about the cam axis (17). Position (5) represents the distance between the line of action and the force at the point of force introduction of the spring element. Position (13) represents the line of bending moment introduction of the cams. (4) represents the torque-force line of action, while position (13) represents the line of bending moment introduction of the cams.Position (23) represents the conical projection relative to the cam width, serving as an adapter part to the adjacent elastic layer elements. The adapter parts can also be omitted if necessary. (D) shows a perspective section through the coupling according to the invention. The cam axis (17) and the coupling axis (18) arranged perpendicular to it are shown here. (E) shows a section (AA) through the coupling of the . Fig. 3 (A) and an enlargement of the area of ​​a spring element (3) which connects the drive pulley (1) to the driven pulley (2). Position (5) in turn represents the distance from the line of action to the force introduction of the spring element, while position (9) represents the distance between the two clutch discs (1)(2). Position (11) indicates the length of the inclined carrier cams (7) as well as the angle of attack (14) relative to the plane of the clutch discs. Finally, position (15) indicates the effective radius of the clutch. The enlarged section on the right-hand side shows the protrusion element (23) in the area of ​​the spring element (3) with its diameter (22), which is significantly larger than the thickness (22) of the carrier cam in this area. Fig. 4shows a comparison between a prior art clutch and the clutch according to the invention: (A): shows a prior art clutch with cams as wide as the diameter of the elastomer elements. (B): shows, in comparison, an embodiment according to the invention with narrower cams.

[0026] It becomes clear that with the conventional clutch with wider cams, the cam angle of attack (14) must also be increased to maintain sufficient space for the interlacing of the opposing cams, while maintaining otherwise identical dimensions, without causing a collision in the intersection area (20). This also increases the bending lever length (5), which leads to a larger bending moment (6).

Claims

1. Elastic cam coupling having cam axes (17), which are arranged perpendicular to the rotation axis of the coupling, for transmitting a torque of a first machine part to a second machine part, comprising a drive disc (1) having support cams (7) projecting outward in a star shape, and a substantially equally-sized driven disc (2) having support cams (8) projecting outward in a star shape, (i) the discs (1)(2) being arranged opposite one another and axially offset from one another and having elements or devices for transmitting a torque from a drive shaft of the first machine part to an output shaft of the second machine part, (ii) the support cams (7) of the drive disc (1) being connected to the support cams (8) of the driven disc (2) via elastic spring elements (3), (iii) the support cams (7) of the drive disc (1) and the support cams (8) of the driven disc (2) having an identical angle of attack (14) of no more than 30° in relation to the axial plane of the two opposite discs (1)(2), and being inclined relative to one another, and (iv) the elastic spring elements (3) being dimensioned such that they protrude beyond the support cams (7)(8) adjacent on both sides with a projection (23), characterized in that the support cams (7) of the drive disc (1) and the support cams (8) of the driven disc (2) are inclined relative to one another by the angle of attack (14) in such a way that they cross without touching one another in their crossing regions (20) during operation, the main bodies of the drive and driven discs lying closely next to one another, as a result of which only small cardanic bending moments (6) around the cam axes (17) occur under load.

2. Elastic cam coupling according to claim 1, characterized in that the size of the projection (23) is defined by the ratio of the diameter (21) of the elastic cantilevered spring elements (3) to the thickness (22) of the support of the adjacent narrower support cams (7)(8), and this ratio is 1.2 to 2.0.

3. Elastic cam coupling according to either claim 1 or claim 2, characterized in that the angle of attack (14) of the support cams (7)(8) is 10°-30°.

4. Elastic cam coupling according to any of claims 1 to 3, characterized in that the projection (23) is cylindrical or conical and is an independent component, an integral part of the elastic spring elements (3), or an integral part of the support cams (7)(8)5. Elastic cam coupling according to any of claims 1 to 4, characterized in that the elastic spring elements (3) are hydraulic spring elements which are arranged and connected to one another on the pressure and relief sides by hydraulic lines and operated in such a way that the elastic spring elements (3) also have a low rigidity in the radial direction, so that the coupling essentially only transmits rotational forces.

6. Elastic cam coupling according to claim 5, characterized in that the hydraulic system has a pressure accumulator or a pressure bladder accumulator for limiting torque.

7. Elastic cam coupling according to any of claims 1 to 6, characterized in that the drive and driven discs (1)(2) each have 3-12 support cams (7)(8) which are connected to one another by twice the number of elastic spring elements (3).

8. Use of an elastic cam coupling according to any of claims 1 to 7 for low-constraint transmission of torques > 5,000 kN × m with low restoring forces in systems, machines and vehicles.

9. Wind turbine comprising a tower, nacelle, rotor and generator / gearbox, characterized in that it has an elastic cam coupling according to any of claims 1 to 7, which is installed in the drive train between the rotor and the generator / gearbox of the system.