WO2011042486A1

WO2011042486A1 - Device for damping and transmitting a torque

Info

Publication number: WO2011042486A1
Application number: PCT/EP2010/064971
Authority: WO
Inventors: Holger Bickelmann
Original assignee: Basf Se
Priority date: 2009-10-09
Filing date: 2010-10-07
Publication date: 2011-04-14

Abstract

The invention relates to a device comprising a first component (10) and a second component (20) which are rotatable about an axis (A) and which at least partially overlap in the direction of the axis (A), characterized in that the first component (10) and the second component (20) are connected in the radial direction by means of a cellular polyisocyanate polyaddition product as a coupling element (30), wherein the circumscribed circle (12) around the cross section of the contact surface between the first component (10) and coupling element (30) is at least 25 per cent larger than the diameter of the inscribed circle (22) at the cross section of the contact surface between the second component (20) and coupling element (30).

Description

The present invention relates to a device comprising a first component and a second component, which are rotatable about an axis and at least partially overlap in the direction of the axis, in which the first component and the second component in radial Direction are connected via a coupling element. Furthermore, the invention relates to a steering system for a motor vehicle with a steering wheel, a steering column and a steering linkage. Furthermore, the invention relates to a drive train with a drive unit and one or more transmission elements that transmit a torque. In addition, the invention comprises the use of the device according to the invention for transmitting a torque. In the transmission of a rotational movement from one component to another component is often the requirement to dampen or decouple disturbing suggestions that act on the components. In order to achieve this, mostly volume-compressible elastomers such as rubber have been used as bearings or couplings between the relevant components.

Thus, in the published patent application DE 195 1 1 273 A1 describes a steering system for a motor vehicle having an elastic member which is arranged in a transmission path from the steering wheel to the wheels of the vehicle. The elastic member consists of a spring element and a damping element, wherein damping coefficient and spring constant are selected in a certain ratio to each other. In one example, the elastic member is made of rubber and vulcanized onto a shaft.

This type of elastic connection usually has a characteristic ratio of stiffness in the axial and radial directions and in terms of torsion. This ratio can be influenced by the choice of the recipe or the geometric design, but this is limited due to the material properties. As an alternative to volume-compressible elastomers, volume-compressible elastomers, for example based on cellular polyisocyanate polyaddition products, are known in principle. They are mainly used as bearing elements or spring elements, which are mainly used for vibration damping. A use of such elastomers for transmitting a torque describes the utility model DE 297 20 240 U1. It discloses a torsionally flexible coupling for a propeller shaft, wherein at two shaft ends in each case a connecting part with substantially radially to the axis of rotation extending flanks and between the flanks of an elastic Spring body is arranged. The elastic spring body may be made of cellular polyurethane. However, this torsionally flexible coupling is structurally complex and takes up a large amount of space. Object of the present invention was to develop a device with which torque can be transferred from one component to another component while damping and decoupling unwanted excitations of the components. The device should be easy to manufacture and be widely adjustable in terms of its properties, such as stiffness.

This object is achieved by the subject matter of the invention, as set forth in claim 1. Further advantageous embodiments of the invention can be found in the dependent claims. Another object of the invention is specified in the independent claims 1 1 and 12. Uses of the articles of the invention are set forth in claims 13 to 15.

The device according to the invention comprises a first component, a second component and a coupling element. The first component and the second component have no common contact surface, but are each connected to the coupling element. Preferably, the first and second components are rigid bodies which may be made of metal, hard plastic, composites or fiber reinforced composites. The fiber-reinforced composite materials may contain glass fibers, carbon fibers or aramid fibers, preference is given to glass fibers. The property that the components have no common contact surface refers to the normal operating range of the device. Securing devices such as stops, e.g. can be provided in the event of material failure of the coupling element, do not contradict the inventive concept.

The first component and the second component are rotatable about an axis, the term "an axis" being understood to mean essentially a common axis of rotation Due to the elastic properties of the coupling element, there may be a slight deviation between the axis of rotation The amount of this deviation may vary during a rotational movement, with deviations of -7 ° to + 7 °, preferably -5 ° to + 5 °, in particular of According to the invention, during a rotational movement, a force is transmitted from one component to the other component via the coupling element, whereby the driving torque can originate either from the first component or from the second component allow, the components are preferably stored or guided in suitable devices, for example in ball bearings n, rolling bearings or plain bearings. The first component and the second component may have different geometries and dimensions. In a preferred embodiment, the first component or the second component or both are a rod-shaped element. In cross section perpendicular to the longitudinal axis, the rod-shaped element can be designed differently, for example, circular, elliptical, triangular, rectangular, square, pentagonal, hexagonal or polygonal, symmetrical or asymmetrical. Preferably, the cross section is substantially circular or rectangular, more preferably square. The cross section may vary over the length of the rod-shaped element, both in its dimension and in shape. In particular, one end or both ends of the rod-shaped element may be shaped differently in shape from the inner part of the element. For example, a rod-shaped element of circular cross-section may have an end having the cross-sectional shape of a square. The cross section may be filled so that the rod-shaped element is made compact from a material. The rod-shaped element may also be hollow, for example in the form of a tube. In a preferred embodiment, the rod-shaped ele- ment is a tube which is made of metal, in particular of a steel.

In a further preferred embodiment, the first component, the second component or both are a socket. Also, the socket can be designed differently in terms of shape and dimension. In cross-section perpendicular to the longitudinal axis, the bush may be, for example, circular, elliptical, triangular, rectangular, square, pentagonal, hexagonal or polygonal, symmetrical or asymmetrical. Preferably, the cross section is substantially circular. Furthermore, the cross section is preferably substantially square. In an advantageous embodiment, the socket is designed so that further devices can be attached thereto, for example, characterized in that the inner surface of the socket is at least partially designed as a thread. Preferably, the bush is made of metal, in particular of aluminum or steel. In a further preferred embodiment, the bush consists of a bent sheet metal, which is not closed as a tube, but has a slot in the direction of the axis and only after being pressed into a corresponding receiving device to a closed socket. Further preferred is a bush made of hard plastic, in particular of a thermoplastic polyurethane material or a reactive polyurethane system.

According to the invention, the first component and the second component are connected via a cellular polyisocyanate polyaddition product as a coupling element. Zellig means in this context that the cells preferably have a diameter of 0.01 mm to 0.5 mm, more preferably from 0.01 mm to 0.15 mm.

Elastomers based on cellular polyisocyanate polyaddition products and their preparation are well known and variously described, for example in EP 62 835 A1, EP 36 994 A2, EP 250 969 A1, EP 1 171 515 A1, DE 195 48 770 A1 and DE 195 48 771 A1.

The cellular polyisocyanate polyaddition products particularly preferably have at least one of the following material properties: a density according to DIN EN ISO 845 of between 200 and 1100 kg / m ³ , preferably between 270 and 900 kg / m ³ , a tensile strength according to DIN EN ISO 1798 of> 2.0 N / mm ² , preferably> 4 N / mm ² , more preferably between 2 and 8 N / mm ² , an elongation at break according to DIN EN ISO 1798 of> 200%, preferably> 230%, particularly preferably between 300 up to 700% and / or a tear strength according to DIN ISO 34-1 B (b)> 6 N / mm, preferably> 8 N / mm, particularly preferably> 10 N / mm. In further preferred embodiments, the cellular polyisocyanate polyaddition product has two, more preferably three of these material properties, particularly preferred embodiments have all four of said material properties.

The preparation is usually carried out by reacting isocyanates with isocyanate-reactive compounds.

In a preferred embodiment, the cellular polyurethane elastomers, based on the isocyanates diisocyanatotoluene (TDI) and naphthylene diisocyanate

(NDI), most preferably based on 2-, 6-diisocyanatotoluene (TODI) and 1-, 5-Naphthylendiisocyanat (5-NDI) prepared.

The coupling elements based on cellular polyisocyanate polyaddition products are usually prepared in a form in which the reactive starting components are reacted together. As forms come here generally conventional shapes in question, for example, metal forms that ensure the three-dimensional shape of the coupling element due to their shape. The preparation of the polyisocyanate polyaddition products can be carried out by generally known processes, for example by using the following starting materials in a one- or two-stage process:

(a) isocyanate,

(b) isocyanate-reactive compounds,

(c) water and optionally

(d) catalysts,

(e) propellant and / or

(f) auxiliaries and / or additives, for example polysiloxanes and / or fatty acid sulfonates. The surface temperature of the mold inner wall is usually 40 to 95 ° C, preferably 50 to 90 ° C.

The production of the moldings is advantageously carried out at an NCO / OH ratio of 0.85 to 1.20, wherein the heated starting components are mixed and brought in an amount corresponding to the desired molding density in a heated, preferably tightly closing mold.

The moldings are cured after up to 60 minutes and thus demoulded.

The amount of the introduced into the mold reaction mixture is usually measured so that the resulting moldings have the density already shown. The starting components are usually introduced at a temperature of 15 to 120 ° C, preferably from 30 to 1 10 ° C, in the mold. The degrees of densification for the production of the molded articles are between 1, 1 and 8, preferably between 2 and 6. The cellular polyisocyanate polyaddition products are expediently prepared by the one-shot process using the low-pressure technique or, in particular, the reaction injection molding technique (RIM). in open or preferably closed molds. The reaction is carried out in particular under compression in a closed mold. The reaction injection molding technique is described for example by H. Piechota and H. Röhr in "Integral Foams", Carl Hanser Verlag, Munich, Vienna 1975; DJ. Prepelka and JL Wharton in Journal of Cellular Plastics, March / April 1975, pages 87-98 and U. Knipp in Journal of Cellular Plastics, March / April 1973, pages 76-84. According to the invention, the first component and the second component overlap at least partially in the direction of the axis. The first component is preferably designed at least in the overlapping region in the form of a tube, wherein the inner diameter of the tube is greater than the outer diameter of the second component. In particular, the first component is a bush, a tube or a bar-shaped element, one end of which is designed as a tube. The term diameter is not to be understood as limiting to a circular shape, but refers to the maximum inner or outer dimensions of the respective cross-section, for example, the edge length in a square cross-section. The cross sections of the first component and the second component in the overlapping region can also be of different shape, for example circular as the inner profile of the first component and square as the outer profile of the second component or vice versa. The coupling element is arranged in the radial direction between the first component and the second component. During a rotational movement of the first component relative to the second component, a force transmission takes place predominantly via the radial contact surfaces between the first component and the coupling element. The coupling element in turn transmits the force predominantly via the radial contact surfaces between the second component and the coupling element to the second component. Depending on the shape of the inner surface of the first component and the outer surface of the second component, the coupling element is subject to different strong forces such as pressure and shear.

The invention improves known devices to the extent that stiffness in the axial and radial directions for different load conditions can be better matched to the particular application. For this purpose, it is necessary that the material thickness of the coupling element does not fall below certain limits. Since the effect does not depend exclusively on the material thickness, but e.g. also from the cross-sectional shape of the components is considered essential to the criterion, the ratio of perimeter to incircle as defined below and explained in more detail in Figs. 3 to 1 1.

Considered is a section perpendicular to the axis, wherein a first component has a smaller outer diameter than the inner diameter of a second component. A circumference is set around the cross section of the contact surface of the first component and coupling element, the diameter of which is selected to be just so small that it completely covers the cross section of the contact surface. Similarly, an in-circle is applied to the cross section of the contact surface of the second component and coupling element, whose diameter is just chosen so large that it still fits in the cross section of the contact surface, without cutting it. According to the invention, the circumference around the cross section of the contact surface of the first component and coupling element is at most 25 percent, preferably 20 percent, particularly preferably 15 percent greater than the diameter of the inscribed circle at the cross section of the contact surface of the second component and coupling element.

The coupling element can be manufactured in different ways. It can be manufactured, for example, as a tubular fabric and then cut to the required length. It can also be designed as a plate and cut to the length and width required as a coupling element. With the aid of the method of water jet cutting, it is easy to realize different profiles of the coupling element. The coupling element can also consist of several individual parts, for example of tube sections or plates of different densities, in order to better adapt the properties in different spatial directions to the requirements. The coupling element must not be continuous in the direction of the axis and in the circumferential direction. It can also contain several individual parts, for Wise strips comprise, which are arranged in the direction of the axis or in the circumferential direction such that there are cavities between them.

The length of the coupling element in the direction of the axis is preferably from 5 to 80 mm, particularly preferably from 10 to 50 mm, in particular from 20 to 40 mm. The radial extent of the coupling element is preferably in the range from 2 to 12 mm, particularly preferably from 3 to 10 mm, in particular from 4 to 8 mm. The diameter of the circumference around the inner component is preferably from 10 to 90 mm, more preferably from 15 to 60 mm, in particular from 20 to 40 mm, wherein the diameter of the inscribed circle is preferably smaller than 75 mm. In a coupling element, whose cross sections of the contact surfaces of the coupling element with the first component and the second component are each circular, the perimeter diameter corresponds to the outer diameter of the inner member and the Inkreisdurchmesser the inner diameter of the outer member.

Coupling element and first component as well as coupling element and second component can be connected to one another in different ways. In a preferred embodiment, the coupling element is a separately manufactured element which is connected to the first component or the second component or both, particularly preferably by gluing.

The bonding can be done by known methods, for example by an adhesive is applied to the surface to be joined of the component or the coupling element and then the component and coupling element are joined together. Preferably, reactive cold or thermosetting two component adhesives are used, e.g. reactive systems based on isocyanates or epoxides or hot melt adhesives, so-called hotmelts. Particular advantages are offered by a class of reactive hot melt adhesives which preferably contain encapsulated isocyanates embedded in a polyol matrix. These hot melt adhesives can be applied, for example, as a powder to the surface to be bonded and melt, whereby they adhere to the surface to be bonded without significantly lose reactivity. This makes it possible to position such pretreated elements to each other without removing the adhesive from the surfaces to be bonded of the elements. By heating the prepositioned elements well above the melting point of the powder break the encapsulated isocyanates and initiate the crosslinking reaction. Such hot melt adhesives are commercially available.

Instead of an adhesive, it is also possible to use a melt film which is applied to the surface to be joined of the component or the coupling element. Subsequently, component and coupling element are joined together and heated. The melted foil melts and forms a durable, solid after cooling Connection. For this purpose, preference is given to using melt foils made of thermoplastic polyurethane (TPU).

In a further preferred embodiment, coupling element and component are bonded by means of a casting resin, which may in particular be a reactive polyurethane system. The use of a casting resin as an adhesive offers the advantage that lower demands on the manufacturing accuracy must be made because the casting resin fills cavities between the component and coupling element and after curing, the elements are permanently and firmly connected.

In a preferred variant of the invention, the coupling element comprises one or more strips, e.g. can be cut by a water jet from a plate. The strips are dimensioned so that they form a closed coupling element in the circumferential direction when installed, with the exception of a small gap. The strips are particularly suitable for being applied to the first component, the second component or both. For this purpose, for example, the first component is fixed in its position relative to the second component, the or the strip loosely placed in the space between the components and molded with a casting resin.

In a further preferred embodiment, the connection between the coupling element and the component is realized in that the coupling element is foamed in its manufacture to the first component or the second component. Of course, the coupling element can be connected in this way with both components. Depending on the material properties of the component, a bonding agent can be applied to the surfaces of the component to be joined before the foaming of the coupling element.

Further preferably, a connection is realized in that the component is connected during its manufacture with the coupling element. Such a method of manufacture is possible, for example, for a component made of a hard plastic, e.g. a thermoplastic polyurethane (TPU) is made. In this case, the separately produced coupling element can be inserted into a mold and then encapsulated or overmolded by known methods. In particular when using a TPU material results due to the material properties a permanent, firm connection between the component and the coupling element. Chemical adhesion promoters can usually be dispensed with in this case.

The TPU materials can also be used in generally known mixtures with other thermoplastics, for example polyolefins, ABS and / or ASA plastics, as well as fillers such as glass fibers. Preference is given to TPU materials with glass fiber admixtures. The TPU can be based on known raw materials, for example, the commonly used isocyanates, polyols, chain extenders, catalysts and excipients. The thickness of the TPU material is preferably from 1 to 15 mm, more preferably from 3 to 10 mm. In a further preferred method for producing a component with simultaneous connection of the component to the coupling element, instead of the TPU material, a reactive polyurethane system is used which can be processed by means of the generally known RIM technology (Reaction Injection Molding) or as a classical casting system. Since this casting resin as described above is also well suited as an adhesive, in a particularly preferred embodiment, a first component is produced by casting or injection molding on the coupling element and in the same operation another, already prefabricated component adhesively connected to the coupling element. In a further preferred embodiment, the component and the coupling element are interconnected by frictional connection in that the minimum and maximum radial dimensions of the components and of the coupling element are selected such that they can be joined together under pretensioning. In the case of overlapping components, in which the inner diameter of the first component is greater than the outer diameter of the second component, the first component is advantageously connected to the coupling element in that the outer diameter of the coupling element is greater than the inner diameter of the first component. Analogously, the inner diameter of the coupling element is advantageously selected smaller than the outer diameter of the second component in a connection with the second component. When joining the coupling element is biased and attached to the component by known methods. The coupling element may also be first connected to the first component or the second component or both and then biased. An example of this is the calibration of a circular, outer first component which is pressed by a diameter-tapering die. As a result of the deformation of the first component, the coupling element is biased in the radial direction. By analogy, an inner second component can be widened, for example, by being pushed onto a mandrel which increases in diameter, which likewise leads to the precompression of the coupling element. The precompression of the coupling element is preferably in the range of 5 to 50%, in particular of 5 to 35%, based on the original, uncompressed volume of the coupling element.

Another type of connection according to the invention between the component and the coupling element is to achieve positive locking via the shaping. This can be achieved for example by the geometric design of the component cross-section, for example in a rectangular inner or outer profile. Furthermore, a form fit can also be achieved via elevations and depressions in the touching upper surfaces of component and coupling element can be realized. The determination of the circumference takes place in this case on the basis of the radially largest extent of the contact surface between the inner component and the coupling element, for example, elevations on the outer surface of the inner component. Similarly, the inscribed circle is determined on the basis of the radially smallest extent of the contact surface between the outer component and the coupling element, for example elevations on the inner surface of the outer component.

Of course, the different types of connection can also be combined, for example, by the connection between the first component and coupling element on bonding and the connection between the second component and coupling element based on adhesion or positive engagement. A positive connection can also be glued in addition. In a further advantageous embodiment of the invention, the coupling element on stiffening elements, which serve to influence the torsional stiffness of the device targeted. Preferably, the stiffening elements are located in the interior of the coupling element. Particularly preferably, they are arranged substantially in the direction of the axis. Such stiffening elements may consist of pins, which may have different lengths and cross-sectional profiles.

In a preferred embodiment, the stiffening elements are produced in the same working step as the connection of the coupling element with at least one component. One possible realization is to initially save cavities in the production of the coupling element. In the connection of the coupling element and the first or second component, a casting resin can be used, on the one hand to make the connection and to fill in the same operation, the cavities in the coupling element. After curing of the casting thus stiffening elements are formed in the coupling element. Compared with the known method of pressing plastic injection as stiffening elements, the solution according to the invention offers the advantage that no separate element has to be produced and an additional working step, such as pressing together with the necessary tools, is eliminated. Another object of the invention relates to a steering system for a motor vehicle, comprising a steering wheel, a steering shaft and a steering gear. According to the invention, at least one device as described above is present in the power transmission path from the steering wheel to the steering gear via the steering shaft to dampen vibrations from the steering wheel and the vehicle interior and to transmit the rotational movement generated by the steering wheel to the steering gear. Vibrations can be registered, for example, by road excitations in the steering system or generated by the components of the steering system itself. The steering shaft may consist of several sections, which are divided for example by universal joints, as explained in more detail in Fig. 13. In a preferred embodiment, the steering shaft or a portion of the steering shaft is a rod-shaped element in the sense of the invention shown above. The coupling element is fastened directly to the steering shaft or a portion of the steering shaft as the first component. The second component may be another portion of the steering shaft, a universal joint or other element in the power transmission path from the steering wheel to the steering gear. The second component can also be a bush, which in turn is connected to a section of the steering shaft, a cardan joint or another element, for example by tight fit after being pressed into or onto a corresponding receiving device.

In a further preferred embodiment, the first component, the second component or both are a socket, which is connected to the coupling element. The socket is designed so that it can be connected by known methods firmly with the steering shaft, a portion of the steering shaft, a universal joint or other element in the power transmission path from the steering wheel to the steering gear. This can be implemented, for example, in that the bushing has as outer bushing a diameter which is larger than the inner diameter of a corresponding receiving device, e.g. a portion of the steering shaft. The connection of socket and e.g. However, section of the steering shaft can also be realized in that the bushing has a thread as an inner bush, via which the portion of the steering shaft is screwed.

Another object of the invention relates to a drive train comprising a drive unit and one or more transmission elements which transmit a torque. According to the invention, at least one of the transmission elements is provided with a device as described above. The power plant may be any type of actuator that provides mechanical power, e.g. Internal combustion engines, electric, hydraulic or pneumatic motors. The transmission elements may be shafts, gears, claws or similar devices that transmit the power of the power plant to other components.

The device according to the invention can be used in a variety of ways, examples being: mechatronic drive trains, eg for transmitting a rotational movement which originates from an electric motor and in which high-frequency components of the torque signal or path excitation are to be decoupled; Decoupling of higher-frequency components from hydraulic torque sources, eg decoupling of so-called Hiss noises, which are excited by the flow of oil in hydraulic systems;

Transmission of torque in mechanical arrangements, e.g. before or after a universal joint, with simultaneous decoupling of higher-frequency

Shares of lateral forces;

Decoupling unwanted axial or radial excitations while transmitting torque, e.g. the reduction of hum due to a natural vibration of a component or the reduction of transmission noise;

Attenuation of large amplitude torque cycling, e.g. in the powertrain of motorcycles;

Electrohydraulic or electromechanical steering systems in which quasi-static or very low-frequency (<1 Hz) rotational motions relevant for driving dynamics are to be transmitted while at the same time reducing the transmission of noise from the servomotors or from the surface of the vehicle to the vehicle interior;

Disconnection of disturbing noises and suggestions from electric motors in hybrid powertrains.

Compared to known devices for transmitting torques, which are based in the majority on a coupling element made of rubber, the invention offers several advantages: The spreading of the torsional stiffness to axial and radial stiffness is both static and dynamic particularly high compared to volume compressible elastomers. As a result, torques can be transmitted in a targeted manner and, at the same time, axial and radial excitations such as vibrations can be better decoupled. A lower axial stiffness facilitates the production of a length compensation, which is particularly advantageous when used in a drive train. The stiffening of the torsional stiffness as a comparison between static and dynamic rigidity is significantly lower than with rubber elements, especially at low amplitudes (<0.5 °).

With the same installation space ratios, maximum angles of rotation and at least the same fatigue strength, higher torsional stiffnesses can be achieved. For torsionally flexible coupling elements, higher fatigue strengths can be achieved. A progressive torque torsion angle characteristic can be achieved similar to rubber elements by geometric measures such as inner and outer profiling or the addition of stiffening elements, but the volume compressibility favors the achievement of high maximum angles of twist and long lifetimes. In addition, there is a weight advantage over known volume-compressible elastomers. Properties such as spreading, damping values and stiffening can be adjusted by means of measures such as radial precompression, profiling of the coupling element and the choice of the bulk density of the cellular polyisocyanate polyaddition product. The component continuum resonances of the component are in much higher frequency ranges than comparable rubber components. This makes it possible to better decouple high-frequency components (greater than 100 Hz) of torsional, radial and axial excitations. Of particular advantage is the use of a cellular polyisocyanate addition product based on NDI as a coupling element due to its fatigue properties under shear and compressive stress, the stiffening properties, its settlement behavior, tear strength, high energy absorption in compression to progression, and the media and temperature resistance.

With reference to the drawings, the invention will be further explained in the following, the drawings being to be understood as schematic representations. They do not limit the invention, for example with regard to specific dimensions or design variants of components.

Fig. 1: Example of an embodiment with circular cross-sections

Fig. 2: Example of an embodiment with square cross-sections

3-5: Square cross-sectional profiles of embodiments according to the invention. FIGS. 6-7: Octagonal cross-sectional profiles of embodiments according to the invention

Fig. 8-10: Combined cross-sectional profiles of embodiments according to the invention

Fig. 1 1: cross-sectional profiles of a further embodiment

Fig. 12: Example of an embodiment with stiffening elements

Fig. 13: Example of a steering system with inventive device

Fig. 14-15: Connection of steering shaft and universal joint in a steering system for

Motor vehicles according to the prior art

Fig. 16-17: Inventive embodiment of a compound of steering shaft and

Cardan joint in a steering system for motor vehicles FIG. 1 shows a schematic diagram of an embodiment of the device 1 according to the invention. A rod-shaped element forms a first component 10, which is rotatable about an axis A. The element may, for example, be a shaft which can be set in a rotational movement about the axis A. In the radial direction outside around the first component 10 around a second component 20 is arranged, which is also rotatable about the axis A. In this exemplary embodiment, the second component 20 is designed in the form of a socket. The intermediate space between the first component 10 and the second component 20 is with a cellular polyisocyanate polyaddition product filled as coupling element 30. If the first component 10 is set in a rotational movement, the torque is transmitted through the coupling element 30 to the second component 20. In the embodiment shown in FIG. 1, the contact surface 11 between the first component 10 and the coupling element 30 and the contact surface 21 between the second component 20 and the coupling element 30, viewed in cross-section perpendicular to the axis A, have the shape of concentric circles. Perimeter and incircle are identical to the respective cross sections.

2 illustrates a schematic diagram of a further embodiment of the device 1 according to the invention. The difference from the embodiment in FIG. 1 is that the cross sections of the contact surfaces of the first component 10 and the second component 20 with the coupling element 30 are substantially square. Only the corners are rounded. How the diameter behaves from circle to circle depends on the respective edge length of the square cross-sectional area.

Fig. 3 shows the contact surface 1 1 of a first component and the contact surface 21 of a second component with the coupling element in cross-section perpendicular to the axis A. The second component surrounds the first component in the radial direction. The outer contour of the second, outer component is not shown. Likewise, the inner contour of the first, inner component is not shown. The space between the two contact surfaces 11 and 21 is filled with elastomer and is referred to below as the elastomer surface 31. The circumference 12 around the outer contour of the cross section of the contact surface 1 1 of the inner member and the inscribed circle 22 to the inner contour of the cross section of the contact surface 21 of the outer member are shown in dashed lines. In the case of the cross-sectional profiles illustrated in FIG. 3, the diameter of the circumference 12 is approximately 73% of the diameter of the inscribed circle 22.

Fig. 4 shows an analogous situation as Fig. 3, but for the special case that perimeter and incircle are identical. In the arrangement of FIG. 5, the diameter of the circumference is greater than the diameter of the inscribed circle, namely by 20% for the dimensions shown concretely. The representations of FIGS. 3 to 5 are to scale, wherein the cross section of the contact surface 1 1 of the inner member with the coupling element is identical in each case.

The illustrations in FIGS. 6 to 7 correspond to those in FIGS. 3 to 4, with the difference that, instead of the square octagonal cross sections of the contact surfaces 11 and 21, they are considered. In the configuration shown in Fig. 6, the diameter of the circumference 12 is about 84% of the diameter of the inscribed circle 22. Fig. 7 shows the special case in which perimeter and inscribed circle are identical. From a 4, it can be seen that, in the case of octagonal cross-sectional profiles, the wall thickness of the elastomer as well as the entire elastomer surface 31 is significantly smaller for the same ratio of perimeter to incircle. In the case of octagonal cross-sectional profiles, it is possible for the circumference 12 to be larger than the inscribed circle 22, but the contact surfaces 11 and 21 approach each other so strongly that the minimum wall thickness can only be maintained for large diameters.

FIGS. 8 to 10 show further examples of embodiments according to the invention. The cross-sectional profiles of the contact surfaces 1 1 and 12 are borrowed in these cases. In FIG. 8, the contact surface 11 between the inner component and the coupling element is square, while the contact surface 21 between the outer component and the coupling element is octagonal. The diameter of the circumference 12 is about 83% of the diameter of the inscribed circle 22. In the arrangement shown in Fig. 9, the cross section of the outer contact surface is circular and therefore identical with its inscribed circle. In Fig. 10, the reverse case is shown that the cross section of the inner contact surface is circular and thus identical to its circumference. In both cases it is common that the diameter of the circumference can not be greater than the diameter of the inscribed circle. Their ratio is determined by the choice of the minimum wall thickness of the elastomer.

However, the embodiments according to the invention are not limited to the abovementioned geometries. A further embodiment of the device according to the invention is shown in Fig. 1 1. The cross-section of the contact surface 21 of the outer component and the coupling element is hexagonal, while the cross section of the contact surface 11 of the inner component and the coupling element represents a quadrangle with concave sides. The circumference 12 is placed around the outer contour of the cross section of the contact surface 11. FIG. 12 shows an embodiment of the device 1 according to the invention which, in addition to a first component 10, second component 20 and coupling element 30, has stiffening elements 41, 42, which serve to increase the torsional rigidity of the coupling element 30. A stiffening element 41 is connected to the first component and encloses it completely. For determining the circumference, the outer contour of the cross-section of the contact surface between the stiffening element 41 and the coupling element 30 is to be used in this case. The further stiffening elements 42 are viewed in cross-section completely enclosed by elastomeric material. Since they are not firmly connected to either the first component 10 or the second component 20, they are not considered when considering the ratio of perimeter to incircle. An advantageous application of the device according to the invention relates to steering systems of motor vehicles, as shown schematically in FIG. Usually, a steering system comprises a steering wheel 51 and a transmission device for transmitting steering inputs by the driver from the steering wheel 51 to the tires 57 of the vehicle. The transmission device comprises a steering gear 52 and a mechanical steering shaft 54, wherein the steering shaft 54 serves to transmit on the steering wheel 51 discontinued rotational movements on an input shaft 59 of the steering gear 52. The steering gear 52 may be mounted on a front axle undercarriage 53 or directly on the body 58 of the vehicle. Frequently, the steering shaft 54 is divided by one or more universal joints 55 in two or more sections. In the shaft sections torsionally flexible couplings 56 may be integrated. In an embodiment of the steering system according to the invention, at least one device according to the invention is present in the power transmission path from the steering wheel 51 via the steering shaft 54 to the steering gear 52, for example as a torsionally flexible coupling 56.

The effect of uneven road surfaces on the vehicle wheels, movements of the steering gear relative to the body or the operation of hydraulic or e- lektrischen units in power steering systems can enter disturbing vibration engineering suggestions in the steering shaft. Such suggestions can be entered in the axial and radial directions and in the direction of rotation about the longitudinal axis of the steering shaft. About the steering shaft, they can be transmitted to the steering wheel and there perceived as unpleasant shocks and vibrations by the driver. The suggestions can propagate in the form of structure-borne noise signals to the steering wheel or via the steering column bearings to other locations in the vehicle interior, where they emit disturbing airborne sound signals as the vehicle occupants. For example, so-called chassis stucco, i. resonance-related relative movements of the subframe to the body or the vehicle wheels lead to unpleasant vibrations on the steering wheel. Furthermore, oil flows in hydraulic steering systems can become noticeable as so-called hiss noises in the vehicle interior.

In the design of steering systems, inter alia, the objectives are pursued that, on the one hand, the most direct possible steering feel is to be achieved and, on the other hand, disturbing vibration-related suggestions of steering wheel and vehicle interior are to be isolated. To achieve a direct steering feel, a high torsional rigidity of the steering shaft in the quasi-static case and in the dynamic case up to about 5 Hz at torsional amplitudes up to 2 ° is advantageous. For the isolation of disturbing vibrations, it is advantageous to achieve the lowest possible torsional rigidity of the steering shaft in the higher-frequency range greater than 5 Hz at torsional amplitudes significantly less than 1 ° and to obtain low stiffnesses in the steering shaft in the axial and radial directions. The constructive implementation of the low axial and radial stiffness in the steering shaft is designed and with the bearing of the steering shaft relative to the body combined, that the axes of rotation of the steering shaft are stably guided and the portions of the steering shaft due to an application of torques are not prone to evasive movements. The design seeks to maximize the quasi-static and low-frequency torsional stiffness to create a direct steering feel, but at the same time just high enough to have the higher-frequency torsional stiffness associated with the design as well as the axial and radial stiffnesses associated with the design adequate insulation of disturbing vibrations and noises is given.

Compared to known solutions, the use of devices according to the invention in steering systems offers the advantage that the ratio of torsional stiffness in the quasi-static case or at low frequencies (less than 5 Hz) for torsional rigidity at higher frequencies (greater than 5 Hz) due to the material properties of the cellular polyisocyanate polyaddition product higher values can accept. Likewise, the ratio of the torsional rigidity to the axial and radial stiffnesses may assume higher values. This allows a better and more individual adjustment of the characteristics of a steering system, in particular a balancing of the conflict of goals between the achievement of the direct steering feeling and the isolation of disturbing suggestions.

example

The invention will be explained in more detail below with reference to a steering system for motor vehicles. Figures 14 and 15 show parts of different steering systems known in the art. A pipe 54 as a portion of a steering shaft is connected via a rubber-metal composite element 60 to a pipe fork 55 as part of a cardan joint. The damping element 60 in Fig. 14 consists of an inner and an outer metal sleeve, which are equal in length and are arranged concentrically with each other. They were elastically bonded together by vulcanizing a rubber layer. The components were then pressed into each other. In Fig. 15, the damping element 61 has an outer sleeve made of metal and is vulcanized directly to the tube 54. Further, stiffening elements 62 in the form of plastic pins are pressed into the rubber layer. The pipe fork 55 facing the end of the tube 54 has a square profile in cross-section and engages in a square recess of the pipe fork 55 a. At rest, the square profiles of tube 54 and pipe fork 55 do not touch. In a rotation of the tube 54 relative to the pipe fork 55, the rubber is twisted in the damping element 60 and 61 and transmits a torque between the tube 54 and tube fork 55. The square profiles act as a limitation of the deflection of a rotary motion, since they touch when the deflection becomes too strong. They thus also serve as a mechanical safeguard in the event of failure of the damping element.

FIG. 16 shows a steering system for motor vehicles with a device according to the invention comprising a tube 54 as a first component 10, an outer sleeve as a second component 20 and a coupling element 30. The tube is made of steel and has an outside diameter of 25 mm. The second component 20 is also made of steel and has a length of 44 mm, an inner diameter of 35.7 mm and a wall thickness of 1, 3 mm. The coupling element 30 was manufactured from a cellular polyisocyanate polyaddition product as a sleeve-shaped elastomer semi-finished product. Its length is also 44 mm with an inner diameter of 29 mm and an outer diameter of 34 mm.

To produce the device, the coupling element 30 between the first part 10 and second component part 20 was inserted and connected by casting with a casting resin firmly with two components. Subsequently, the device was pressed by a tapered die to taper the outer metal bush in the radial direction. As a result, the coupling element 30 was biased in the radial direction. 17 shows a further embodiment according to the invention, in which the coupling element 30 is produced as a plate-shaped elastomer semifinished product. The outer, second component 20 is designed as a bush made of a bent sheet metal. The sheet is not closed as a tube, but has a slot in the axial direction, which is closed only after being pressed into a corresponding receiving device.

In comparison with conventional rubber-metal composite elements, the devices according to the invention have the advantages already mentioned above, in particular a lower ratio of dynamic twist resistance to quasi-static torsional rigidity. In addition, they are easy to manufacture and can be flexibly adapted to the respective requirement profile.

Claims

claims

Device comprising a first component (10) and a second component (20), which are rotatable about an axis (A) and at least partially overlap in the direction of the axis (A), characterized in that the first component (10) and the second component (20) in the radial direction via a cellular polyisocyanate polyaddition product as a coupling element (30) are connected, wherein the circumference (12) around the cross section of the contact surface of the first component (10) and coupling element (30) is greater than 25 percent greater as the diameter of the inscribed circle (22) at the cross section of the contact surface of the second component (20) and coupling element (30).

The device of claim 1, wherein the cross-sections of the surfaces on which the first component (10) and coupling element (30) or second component (20) and coupling element (30) make contact are substantially circular or rectangular.

Device according to claim 2, wherein the cross section of the contact surface between the first component (10) and coupling element (30) and the cross section of the contact surface between the second component (20) and coupling element (30) are substantially square.

Apparatus according to claim 1 to 3, wherein the first component (10) or the second component (20) is a bush made of metal or hard plastic.

Apparatus according to claim 1 to 4, wherein the first component (10) or the second component (20) is a rod-shaped element, at one end of a coupling element (30) is present.

Apparatus according to claim 1 to 5, wherein the diameter of the circumference (12) of 10 to 90 mm, preferably from 15 to 60 mm, in particular from 20 to 40 mm.

Device according to claim 1 to 6, wherein the connection between the first component (10) and coupling element (30) or second component (20) and coupling element (30) is realized by adhesion by the minimum and maximum radial dimensions of the components (10, 20 ) and the coupling element (30) are selected so that they are mutually fügbar under bias.

Apparatus according to claim 1 to 7, wherein the connection between the first component (10) and coupling element (30) or second component (20) and coupling Element (30) is realized by gluing, in particular with a casting resin as an adhesive.

Apparatus according to claim 1 to 8, wherein the connection between the first component (10) and coupling element (30) and / or the connection between the second component (20) and coupling element (30) is realized in that the coupling element (30) in its manufacture has been foamed to the first component (10) and / or the second component (20).

Apparatus according to claim 1 to 9, wherein the coupling element (30) stiffening elements (41, 42) in the coupling element (30) which are arranged substantially in the direction of the axis (A).

Steering system for a motor vehicle comprising a steering wheel (51), a steering shaft (54) and a steering gear (52), characterized in that in the power transmission path from the steering wheel (51) via the steering shaft (54) to the steering gear (52) at least one device according to one of claims 1 to 10 is present.

Drive train comprising a drive unit and one or more transmission elements which transmit a torque, characterized in that at least one transmission element comprises a device according to one of claims 1 to 10.

Use of a device according to one of claims 1 to 10 for transmitting a torque from a first component (10) to a second component (20).

Use of a device according to one of claims 1 to 10 for transmitting a torque from a steering wheel to the steering linkage in a motor vehicle.

15. Use of a device according to one of claims 1 to 10 for transmitting a torque from a drive unit to a transmission element in a drive train.