Bearing-shaft assembly and method for operating a bearing-shaft assembly

Abstract

The invention relates to a bearing-shaft assembly comprising: a) at least one shaft (1) which rotates or can rotate about a rotational axis (A) and which is mounted in at least one bearing (2, 12), in particular a bearing that is arranged coaxially to the rotational axis (A), and b) at least one clamping element (6) for exerting a clamping effect or a clamping force between the shaft (1) and the bearing (2) or a receiving element (8), wherein c) the at least one clamping element (6) is actuated or can be actuated or is activated or can be activated, in particular by means of a control unit (24), such that by increasing the clamping effect or clamping force, the rigidity of the bearing-shaft assembly is increased or can be increased and / or the resonance range and / or the natural frequency of the bearing-shaft assembly is shifted or can be shifted.

Description

[0001] Title: BEARING-SHAFT ASSEMBLY AND METHOD FOR

[0002] DRIVE OF A BEARING-SHAFT ASSEMBLY

[0003] Description

[0004] The present invention relates to a bearing-shaft assembly and a method for operating a bearing-shaft assembly. In particular, the invention relates to a bearing-shaft assembly in combination with an electric motor.

[0005] Various bearing-shaft assemblies (or bearing-shaft units) are known in mechanical engineering. Electric motors, spindle units and high-speed shaft-bearing systems are usually constructed according to the fixed-loose bearing principle, in which the shaft is clearly positioned radially and axially in the axial direction by a fixed bearing on the one hand, and is also supported somewhat movably in the axial direction by a loose bearing on the other. This allows thermally and / or mechanically induced (axial) displacements of the shaft to be compensated for. In known designs of such loose bearings, rolling bearings are installed in a sliding bush and thermally and / or mechanically induced axial displacements of the shaft can be compensated for without destroying the rolling bearings due to excessive surface pressures. In order to be able to implement the sliding function, loose bearings do not have a high level of axial and radial rigidity due to the required sliding gap.

[0006] Undesirable and damaging vibrations can occur during operation in rotating shafts of machines and motors and in the bearings and components coupled to the shaft. At critical speeds or close to the natural frequency, a machine part or the entire machine begins to vibrate in resonance. Depending on the geometry and mass distribution, a machine has one or more critical speeds or natural frequencies. The excitation of vibrations at the critical speed results in a vibration maximum in terms of vibration amplitude and vibration velocity. The effects of this type of excitation are reduced by high-precision balancing, damping suspension or by operating at speeds far from the critical speed, i.e. outside the resonance range, and by passing through the critical speed particularly quickly when starting up.However, even these measures cannot completely prevent unwanted vibrations, especially not with the known rolling bearing systems with fixed-loose bearing arrangements.

[0007] An example of the problem of such unwanted vibrations is test benches for testing electric drivetrains in motor vehicles, which typically include an electric motor as the drive, whose vibrations can be transmitted to a test specimen. The publication DE 10 2020 214 884 B4 describes a drive unit for a drivetrain test bench for testing electric drivetrains with an electric motor. A specific configuration of a support device for the electric motor is used for improved vibration damping.

[0008] It is an object of the invention to provide a bearing-shaft assembly, a method for operating a bearing-shaft assembly and an electric motor with a bearing-shaft assembly, in each of which the vibration behavior during operation can be positively influenced.

[0009] The object is achieved in one embodiment according to the invention by a bearing-shaft assembly (or: bearing-shaft unit) comprising: a) at least one shaft rotatable or rotating about an axis of rotation, which is mounted in at least one bearing, in particular arranged coaxially to the axis of rotation, b) at least one clamping element for exerting a clamping effect or clamping force acting between the at least one bearing and at least one receiving element, in particular a bearing plate, wherein the at least one bearing or bearings is or are arranged between the at least one receiving element and the shaft, in particular coaxially to the axis of rotation, and / or for exerting a clamping effect or clamping force acting between the shaft and the at least one bearing, c) wherein the at least one clamping element is controllable or controlled (or: activatable or activated), in particular by means of a control unit,that by increasing the clamping effect or clamping force, the rigidity of the bearing-shaft assembly can be or is increased and / or a resonance range and / or a natural frequency of the bearing-shaft assembly can be or is shifted.

[0010] Instead of the term "bearing-shaft assembly," the term "bearing-shaft unit" or "shaft-bearing system" can be used equally in all embodiments. Unless otherwise defined, "radial" is understood to mean a direction radial or perpendicular to the shaft's axis of rotation, and "axial" is understood to mean a direction axial to, along, or parallel to the shaft's axis of rotation.

[0011] Forces acting on or in the bearing (bearing forces) and clamping forces should be understood in particular as forces acting radially to the shaft's axis of rotation, particularly in the direction of the shaft or the receiving element. However, the forces acting on the bearing can also have components in other directions, for example, in the axial direction. The increased clamping force or clamping effect increases, in particular, the rigidity of the components clamped together in this way, in particular the bearing and receiving element (for bearing and / or shaft) or the bearing and shaft, or all three, and thus the entire bearing-shaft assembly.

[0012] The clamping element can also be referred to or designed as a clamping device or clamping mechanism or tensioning element or device or fixing element or device and can be implemented in particular by means of mechanical or electromechanical drives or actuators with (in particular radial) pressure or force build-up, e.g. by means of wedge mechanisms or also by means of hydraulic or pneumatic pressure actuators.

[0013] Rolling bearings, especially ball bearings or roller bearings, are preferred. However, the bearing can also be of a different type, such as an air bearing, gas bearing, fluid bearing, or plain bearing.

[0014] In one embodiment, at least one or each bearing comprises rolling elements, in particular balls, which are held between a bearing inner ring and a bearing outer ring.

[0015] In one embodiment, at least two bearings are provided, mounted one behind the other axially relative to the rotational axis. A common clamping element can be provided for the bearings, or a separate clamping element can be provided for each bearing.

[0016] In a preferred embodiment, at least one receiving element, in particular a bearing plate, is provided, and the bearing(s) is / are arranged between the shaft and the receiving element, in particular coaxially to the axis of rotation. The receiving element is preferably arranged radially outside the shaft. A mounting block can also be attached to an end face of the receiving element.

[0017] In particular, a bearing shield of an electric drive machine or an electric motor can serve as the receiving element, but also another suitable part of a machine housing or frame of the bearing-shaft assembly or of an electric drive machine.

[0018] In an advantageous embodiment, the bearing or at least one bearing comprises a sliding bushing in the manner of a floating bearing, and the (at least one) clamping element is integrated into the sliding bushing or formed with the sliding bushing. The clamping element is thus developed and further developed based on or integrated into a sliding bushing of a known floating bearing by providing an adjustable or controllable clamping function.

[0019] In an advantageous embodiment, the or at least one clamping element is a hydraulically or pneumatically actuated or activatable clamping element.

[0020] Preferably, the or each or at least at least one clamping element, in particular in a sleeve-shaped or ring-shaped section, has at least one cavity (or: a hollow space) which is filled or can be filled with a hydraulic medium and can be subjected to a hydraulic pressure in the hydraulic medium. For this purpose, a hydraulic unit is preferably provided which is connected to the at least one cavity via at least one hydraulic line and to the control unit via at least one control line. Due to the hydraulic pressure in the cavity, a region of the clamping element, in particular a membrane-like region, lying between the cavity and the bearing can be pressed or pushed or pressed or pressed against the bearing, in particular in the radial direction. This occurs in particular after an initial expansion movement to overcome a radial play and subsequent contact with the bearing, preferably its outer ring.Due to the hydraulic pressure, the clamping pressure or clamping force of the clamping element can now be exerted or is exerted on the bearings and thus the shaft.

[0021] The clamping forces or clamping pressures exerted by a given hydraulic pressure can also be adjusted or designed by the number, design, and arrangement of the cavity(ies) in the clamping element and by the design of the contact surfaces between the clamping element and the bearing(s). The cavity can be formed, in particular, in the sleeve-shaped section over the entire circumference of the clamping element. Alternatively, the cavity can be formed from individual chambers or partial cavities distributed over the circumference of the clamping element and connected to each other via channels.

[0022] In further embodiments, at least one or each clamping element is an electrically or electromechanically actuated or activatable clamping element, in particular a wedge clamping element or a clamping sleeve.

[0023] It can be particularly advantageous if the clamping element is manufactured using a 3D printing process. In particular, the clamping element can be made of a metal, a ceramic material, or a polymer material.

[0024] In a preferred embodiment, the bearing-shaft assembly has at least two operating states. In a first operating state, the clamping element is arranged with a slight radial play relative to the bearings, in particular corresponding to a floating bearing, and exerts no or only a slight clamping force, so that a first stiffness and / or a lower first natural frequency or a first resonance maximum results or is set at a first critical speed. In at least one second operating state, however, the clamping element exerts a higher clamping force than in the first operating state, so that a second stiffness that is higher than the first stiffness results and / or a second natural frequency that is higher than the first natural frequency or a second resonance maximum that is at a second critical speed that is higher than the first critical speed results or is set.Preferably, the control unit switches between the operating states by controlling the clamping element and adjusting its clamping force, thereby shifting the resonance range and / or the natural frequency of the bearing-shaft assembly.

[0025] The control unit can be initiated manually or operated automatically using a sequence control system. The control unit can, for example, be equipped with a programmable microcontroller.

[0026] In a particularly advantageous embodiment, the clamping element or the clamping force is controlled or adjusted depending on at least one or more operating variables or operating parameters, wherein the operating variable or the operating parameter preferably comprises at least one or more of the following:

[0027] (i) a vibration, preferably a vibration amplitude or a vibration velocity, in the bearing-shaft assembly or a coupled component (which allows resonances or natural frequencies to be detected and avoided in a timely manner)

[0028] (ii) an operating temperature of the shaft and / or bearing (to avoid excessive heating)

[0029] (iii) the speed of the shaft

[0030] (iv) a mechanical stress. For this purpose, at least one sensor or a combination of sensors is advantageously provided for detecting one or more of these operating variables or operating parameters, wherein the sensor(s) are preferably arranged in or on the bearing-shaft assembly, in particular

[0031] (i) at least one vibration sensor,

[0032] (ii) alternatively or additionally at least one temperature sensor,

[0033] (iii) alternatively or additionally at least one speed sensor,

[0034] (iv) alternatively or additionally, at least one mechanical stress sensor.

[0035] It is particularly expedient if the control unit switches between the operating states depending on one or more of the operating variables or operating parameters or on one or more of the sensor signals of one or more of the sensors, in particular when a critical threshold value, e.g. with regard to a vibration parameter or with regard to the temperature, is reached.

[0036] The object of the invention is also achieved by an electric motor which is connected to a bearing-shaft assembly according to the invention, wherein the motor shaft is the shaft in the bearing-shaft assembly.

[0037] This allows an electric motor to be provided with particularly smooth running, especially at very high speeds.

[0038] The object of the invention is further achieved by a method for operating a bearing-shaft assembly according to an embodiment of the invention, comprising the following steps: a) accelerating a rotatable shaft of the bearing-shaft assembly; b) detecting or monitoring a vibration parameter of an undesired vibration of the bearing-shaft assembly, such as a vibration amplitude or vibration velocity; c) determining whether the vibration parameter reaches a critical threshold value; d) upon reaching the critical threshold value, changing the stiffness of the bearing-shaft assembly and / or shifting the resonance range and / or a natural frequency of the bearing-shaft assembly, in particular by means of the at least one clamping element.

[0039] Preferably, the acceleration of the shaft is carried out in a first operating state with the first stiffness and / or the lower first natural frequency or the first resonance maximum at the first critical speed, and upon reaching the critical threshold value, switching is carried out to at least the second operating state, which has the second stiffness which is higher than the first stiffness, and / or the second natural frequency which is higher than the first natural frequency, or the second resonance maximum which is at the second critical speed which is higher than the first critical speed.

[0040] Advantageously, when the speed of the shaft in the second operating state is further increased and the critical threshold value is reached again, the system switches back from the second operating state to the first operating state.

[0041] In a further embodiment, the bearing-shaft assembly is operated in the second operating state, and by regularly, preferably briefly, switching to the first operating state, the load on the clamping element and / or the bearing-shaft assembly is relieved. For example, the time spent operating in the second operating state can be four to eight times the time spent operating in the first operating state. This measure has proven useful in preventing unwanted jamming or wedging of the clamping element during operation, while still allowing thermal expansion of the shaft. Further advantageous embodiments and developments according to the invention also emerge from the respective dependent patent claims and from the following description.

[0042] The invention will be further explained below using exemplary embodiments with reference to the drawings. Each of these shows a schematic representation:

[0043] FIG 1 is a diagram illustrating a relationship between vibration velocity and rotational speed in a bearing-shaft assembly;

[0044] FIG 2 shows a sectional view of a bearing-shaft assembly according to the invention;

[0045] FIG 3 is a sectional view of a bearing-shaft assembly corresponding to FIG. 2 with associated control components;

[0046] FIG 4 is a diagram illustrating the variation of the stiffness of the bearing-shaft assembly over time t;

[0047] Corresponding parts and sizes are provided with the same reference numerals in FIGS. 1 to 4.

[0048] FIG. 1 shows a diagram illustrating the relationship between a vibration velocity v of a bearing-shaft assembly and the rotational speed n of a shaft of the bearing-shaft assembly. Such a relationship exists particularly in a bearing-shaft assembly as shown in FIG. 2, with a shaft 1 and at least one bearing 2, in particular a floating bearing, for the shaft 1.

[0049] The vibration velocity v, specified in millimeters per second, at which the bearing-shaft assembly vibrates, correlates with the speed n at which shaft 1 of the assembly rotates or is driven, which can be specified in 1 / s or rpm. Likewise, the vibration amplitude at which the bearing-shaft assembly vibrates correlates with the speed n of shaft 1.

[0050] Curves (1) and (2) show a typical dependence of the vibration velocity v of the bearing-shaft assembly on the shaft speed n, in particular of shaft 1, for different stiffnesses S of the bearing-shaft assembly. Curve (1) illustrates the vibration behavior of a bearing-shaft assembly with a lower stiffness S = Si. Curve (2) illustrates the vibration behavior of a bearing-shaft assembly with a higher stiffness S = S2, where S2 > Si.

[0051] Generally speaking, stiffness S is the resistance of a body to elastic deformation imposed by external load, i.e., force and / or moment, and is determined by the body's material and its geometry. When considering the stiffness S of the bearing-shaft assembly, it therefore depends on the respective stiffnesses of the individual components of the bearing-shaft assembly and how (firmly) the individual components are connected to one another.

[0052] In curve (1), which shows the vibration behavior of the bearing-shaft assembly with the lower stiffness Si, the vibration velocity v increases with increasing speed n, starting from a low vibration velocity vl at a lower speed no and then reaching a larger value v2 (with v2 > vl) of the vibration velocity v at a point PI = (ni , v2) at a speed ni.

[0053] This value v2 of the vibration velocity is already considered a threshold (or limit) that should not be exceeded. In other words, a desired or maximum permissible range of vibrations, expressed here by the vibration velocity v, should lie between vl and a maximum of v2. Within the subsequent speed range or interval [ni, nz] between this speed ni as the lower interval limit and a speed nz as the upper interval limit with nz > ni, the vibration velocity v increases even more steeply, and a resonance maximum MA is reached and a resonance range lying around this resonance maximum MA.

[0054] The resonance maximum MA occurs at a critical speed nA, with ni < nA < nz, at which the bearing-shaft assembly oscillates at its natural frequency or resonance frequency and at the maximum vibration velocity vmax, i.e., MA = (nA , vmax). In the range of the natural frequency, the so-called resonance range, natural vibrations of the assembly occur, leading to undesirably high vibration velocities v and high vibration amplitudes.

[0055] After passing through the critical speed nA and a further increase in the speed n > nA, the vibration speed v decreases again and then, at the upper speed nz as the upper interval limit at point P2, again falls below the threshold value v2 of the vibration speed v and remains again below v2 for n > nz.

[0056] The speed range [ni, nz] between the speeds ni and nz is thus a range or interval in which the vibration velocity v is above the permissible threshold value v2 and is therefore considered too high. A speed n in this speed range [ni, nz] for a given stiffness Si of the system, in particular of the bearing-shaft assembly, should therefore not be assumed at all or only for as short a time as possible.

[0057] The second curve (2) in FIG 1 shows the vibration behavior of the bearing-shaft assembly at the higher stiffness Sz. Curve (2), like curve (1), starts at the low vibration velocity vl at the lower speed no, but at speed ni at point P3 is barely above the initial vibration velocity vl and remains well below the critical threshold value v2 of the vibration velocity v over the entire speed range [ni , nz]. Curve (2) only reaches this critical threshold value v2 at point P4 = (ns , v2) at a speed ns that is greater than the speed nz (ns > nz), i.e. above the speed range [ni , nz].

[0058] In curve (2) too, the vibration velocity v increases even more steeply within the subsequent speed range [ns , n4] between the speed ns and the speed n4 with ns < n4 and a resonance maximum MB = (nB , vmax) is reached again in a resonance range at a critical speed nB, with ns < HB < n4, and subsequently with a further increase in the speed n > nB the vibration velocity v decreases again and then at the upper speed n4 at the point P5 = (n4 , v2) again falls below the threshold value v2 of the vibration velocity v and then remains below v2 again for n > n4.

[0059] The resonance range with the maximum MB in curve (2) with the higher stiffness Sz is therefore at a higher critical speed nB > nA than the maximum MA in curve (1) with the lower stiffness Si.

[0060] These relationships with different resonance ranges or critical speeds nB > nA at different stiffnesses Sz > Si are now implemented in a technical solution in a new and advantageous manner according to the invention.

[0061] A technical possibility is provided for adjusting and controlling the stiffness of the bearing-shaft assembly from the first stiffness Si to the second, higher stiffness Sz, and vice versa, even during operation. This is achieved in the bearing by increasing the clamping effect or clamping force or bearing force between the bearing and the shaft by means of at least one clamping element or clamping device (or: tensioning element or device, locking element or device).

[0062] FIG 2 shows an embodiment of an advantageous hydraulic clamping element on an advantageous loose bearing with ball bearings and a sliding bushing further developed into a clamping element.

[0063] In addition to hydraulic pressure actuators as the clamping element, the invention can be implemented with other embodiments of the clamping element, in particular with other clamping mechanisms, e.g., using mechanical or electromechanical drives or actuators with radial pressure or force build-up, e.g., using wedge mechanisms and / or clamping sleeves with clamping nuts, or even using pneumatic pressure actuators. Other embodiments of floating bearings are also possible, e.g., with (other) deep groove ball bearings, spherical roller bearings, cylindrical roller bearings, toroidal roller bearings, etc.

[0064] The illustration in FIG 2 is cut according to a vertical sectional plane along the rotational axis A of the rotatable shaft 1. On the underside of the assembly (not shown), the components are essentially identical in structure to those on the top side of the assembly shown, or are essentially rotationally symmetrical to the rotational axis A.

[0065] The bearing-shaft assembly shown in FIG 2 comprises a shaft 1 rotatable about a rotation axis A, in particular a drive machine shaft or electric motor shaft, which is rotatably supported in two bearings 2 and 12 arranged one behind the other axially to the rotation axis A and mounted coaxially to the shaft 1 with respect to the rotation axis A. The first bearing 2 comprises rolling elements, in particular balls, 3, which are held between a bearing inner ring 4 and a bearing outer ring 5, and the second bearing 12 comprises rolling elements, in particular balls, 13, which are held between a bearing inner ring 14 and a bearing outer ring 15. The two bearings 2 and 12 are arranged radially between the shaft 1 and a clamping element 6.

[0066] The clamping element 6 is designed and further developed based on or integrated into a sliding bushing of a known floating bearing by providing an adjustable or controllable clamping function. Such a sliding bushing has minimal radial play with respect to the bearings 2 and 12 or, even when free of play, exerts at least only a minimal radial and thus also axial clamping effect or clamping force via the bearings 2 and 12 on the shaft 1, so that the mounted shaft 1, as is usual with a floating bearing, enjoys a certain degree of freedom from displacement or expansion in the axial direction.

[0067] The sliding bushing or clamping element 6 is now in turn held within a receiving element 8, in particular the bearing shield. A mounting block (or end flange) 22 is preferably fastened or arranged on the end face of the bearing shield or receiving element 8 and the sliding bushing 6 as well as the outer ring 5 of the bearing 2, as can be seen, for example, in FIG. 3. The two bearings 2 and 12 thus together form a rolling bearing for the shaft 1, which, by means of the sliding bushing (and the play or sliding gap provided by it) of the clamping element 6, is basically designed as a loose bearing for the shaft 1 within the receiving element 8, thus allowing the shaft 1 a certain axial displacement to compensate for the distance. In other words, the clamping element 6 is preferably sleeve-shaped or annular or has a sleeve-shaped or annular section.In a further development of the sliding bush as a clamping element 6 according to the invention, an adjustability of the bearing pressure or the bearing force, at least the radial bearing pressure or the radial bearing force, is provided by the clamping effect and thus the rigidity of the bearing-shaft assembly and thus a shifting of the natural frequency or critical speed as already described, in particular with reference to FIG 1.

[0068] At least one cavity (or hollow space) 7 is provided in the sliding bushing or the sleeve- or ring-shaped section of the clamping element 6, which cavity is filled or can be filled with a hydraulic medium and can be subjected to hydraulic pressure in the hydraulic medium. This embodiment can be manufactured, in particular, using additive manufacturing (3D printing).

[0069] Due to the hydraulic pressure in the cavity 7, the membrane-like region of the clamping element 6 located between the cavity 7 and the bearing 2 or 12 or the receiving element 8 can be pressed radially outwards or inwards. As a result, this membrane-like region of the clamping element 6 generally initially overcomes the radial play or sliding gap in an expansion movement and then, due to the hydraulic pressure, exerts a clamping pressure or a radial clamping force of the clamping element 6 on the receiving element 8 and / or on the bearings 2 and 12, in particular their outer bearing rings 5 ​​and 15, and thus also via the inner bearing rings 4 and 14 on the shaft 1. This clamping fixes the shaft 1 axially or creates axial clamping forces or holding forces. These radial and axial clamping forces then increase the rigidity of the bearing-shaft assembly.

[0070] The clamping forces or clamping pressures exerted by a predetermined hydraulic pressure can also be adjusted or designed by the number, design and arrangement of the cavity(ies) 7 in the clamping element 6 and by the design of the contact surfaces between the clamping element 6 and the bearings 2 and 12 or their outer rings 5 ​​and 15 and / or the receiving element 8.

[0071] The cavity 7 can be formed, in particular, in the sleeve-shaped section over the entire circumference of the clamping element 6. Alternatively, the cavity can be formed from individual chambers or partial cavities that are distributed over the circumference of the clamping element 6 and connected to one another via channels. In addition, the cavity 7 can be separated from the environment by an outer membrane forming the radially outer surface of the clamping element 7 or of the sleeve-shaped section. The outer membrane is pressed radially outward and spatially displaced radially outward when the cavity 7 is subjected to a pressure-transmitting medium. In this way, the clamping force is transmitted radially outward through the membrane to the receiving element 8 and supported by it.

[0072] According to the embodiment of FIG. 3, a hydraulic unit 25 is provided for generating and adjusting the hydraulic pressure. This hydraulic unit 25 is hydraulically connected to the at least one cavity 7 in the clamping element 6 via a hydraulic line 17 and feeds the hydraulic medium at the specified hydraulic pressure. The hydraulic medium is generally a hydraulic oil, but can also be another fluid, e.g., a silicone oil.

[0073] Even if in the exemplary embodiment a clamping element 6 is assigned to several bearings 2 and 12, each bearing 2 and 12 can also be assigned its own clamping element for individually adjusting the clamping force.

[0074] The adjustment of the hydraulic pressure in the at least one cavity 7 and thus of the stiffness is preferably carried out depending on certain operating variables or parameters, which are measured by means of corresponding sensors.

[0075] In particular,

[0076] (i) Sensor signals of a speed sensor 9 for the measured current speed n of shaft 1 and

[0077] (ii) sensor signals of a temperature sensor 10, which is arranged on or in the clamping element 6 near the pressing surface to the bearings 2 and 12 for monitoring the temperature at the bearings 2 and 12, and

[0078] (iii) Sensor signals of a vibration sensor 11, which can be arranged, for example, on the receiving element 8 or on the mounting block 22 and measures the current vibrations, in particular vibration amplitudes and / or vibration frequencies or vibration velocities, are generated and evaluated.

[0079] The temperature sensor 10 is arranged spatially close to the rolling bearing 2 and 12, in which considerable heat is generated during operation due to the friction in the bearing.

[0080] Sensors 9, 10, and 11 are each connected via a sensor signal line 23 to a control unit 24, which evaluates the sensor signals and generates control signals depending on at least one of the sensor signals. The control signals are transmitted to the hydraulic unit 25 via a control line 26. The sensor signals and the control signals can be analog or digital signals.

[0081] The control unit 24 can control the hydraulic unit 25 electrically or pneumatically, so that the hydraulic unit 25, in turn, supplies the cavity 7 with hydraulic fluid at a specific pressure via the hydraulic line 17. The hydraulic pressure and thus the clamping pressure or clamping force of the clamping element 6 can be varied continuously or switched between two values ​​in several stages or simply in binary mode.

[0082] FIG 4 shows a switching between a first operating state BZ1 with a low clamping pressure or a low clamping force, which can also be zero, i.e. in particular a deactivated or switched off clamping element 6, and a second operating state BZ2 with a significantly higher clamping pressure or a significantly higher clamping force, i.e. in particular an activated or switched on clamping element 6. In the first operating state BZ1, the bearing-shaft assembly assumes a lower value of the stiffness Si, since the bearing 2 and 12 with the sliding bush 6 essentially functions like a conventional floating bearing due to the low or practically non-existent (hydraulic) clamping pressure or the low or practically non-existent (hydraulic) clamping force and allows the shaft 1 a certain axial displacement.In the second operating state BZ2, however, the bearing-shaft assembly now assumes a higher value of stiffness S2 due to the higher (hydraulic) clamping pressure or the higher (hydraulic) clamping force exerted in the connection from the shaft 1 via the bearing 2 and 12 and the clamping element 6 to the receiving element 8. The switching according to FIG 4 is carried out by the control unit 24, which gives the hydraulic unit 25 the command via the control line 26 to increase the hydraulic pressure in the cavity for switching from operating state BZ1 to operating state BZ2 and vice versa to decrease it for switching from operating state BZ2 to operating state BZ1.

[0083] These two stiffness values ​​Si and S2 can now be used for curves (1) and (2) according to FIG. 1 to shift the resonance range and the natural frequency or critical speed, respectively, by selecting the hydraulic pressure difference according to the desired shift of the maximum MA at the critical speed nA in curve (1) to the maximum MB at the critical speed nB in curve (2) with the higher stiffness S2. This assignment is usually determined and specified empirically for a given bearing-shaft assembly with or without appropriately coupled components.

[0084] In other words, the targeted clamping of the sliding bushings with integrated rolling bearings to regulate the system stiffness and the resulting vibration amplitudes allows natural frequencies to be shifted and traversed as required. The stiffness can be actively regulated using the clamping mechanism to shift the natural frequencies of shaft-bearing systems and expand the usable speed range. To this end, sliding bushings, in particular, are held in a non-critical position for the rolling bearings using clamping mechanisms, and the stiffness of the connection between the rolling bearing and the bearing shield is specifically regulated. This changes the system stiffness, increases the natural frequencies, and decreases the vibration amplitudes within the previously specified speed range. The maximum speed of the clamped shaft-bearing system can be increased without damage to the rotating and stationary components.It is now also possible to enter previously critical speed ranges and, depending on the system design, continue to operate through them. Furthermore, depending on the design of the shaft-bearing system, it is possible to deactivate the clamping again after passing through the previous natural frequency range and continue operating at a supercritical speed.

[0085] In an advantageous embodiment according to the exemplary embodiment in FIG. 1 in combination with FIG. 4, an operating method can follow the following control of the stiffness and thus the vibration velocity as a function of the rotational speed by means of the clamping effect or the hydraulic pressure. Preferably, the rotational speed n is continuously measured with the rotational speed sensor 9 and the vibration velocity v with the vibration sensor 11.

[0086] When increasing the speed n, one initially follows curve (1) with the low stiffness Si in the first operating state BZ1 with a normal floating bearing up to point PI at the speed ni and the critical threshold value v2 of the vibration velocity. Then, the system switches to the second operating state BZ2 with the high stiffness S2, thus falling to point P3 on curve (2). Now, with the speed n continuing to increase, one follows curve (2) with the higher stiffness S2 over the entire speed range [ni, n2], thus avoiding the resonance region around the maximum MA and remaining below the critical threshold value v2.When the critical threshold value v2 on the curve (2) is reached at point P4 at the speed ns, the system switches back to the first operating state BZ1, drops from point P4 to point P6 on the curve (2) and follows the curve (1) again, thus avoiding the resonance range around the maximum MB, so that the vibration speed remains below the critical threshold value v2 over the entire speed range.

[0087] In embodiments, the bearing-shaft assembly can be transferred from the first operating state BZ1 to the second operating state BZ2, for example with the aid of the clamping element 6. In the first operating state BZ1, the bearing-shaft assembly has a first, lower stiffness Si. If the measured vibration of the bearing-shaft assembly rises above a threshold value shortly before or within a speed range, the bearing-shaft assembly is transferred from the first to the second operating state BZ2, in which a second, higher stiffness S2 applies. In the second operating state BZ2, a critical speed range is bypassed. The critical speed, which would apply to the bearing-shaft assembly with lower stiffness Si, is passed through without or with a significantly lower vibration maximum.

[0088] When leaving the critical speed range, the bearing-shaft assembly is returned to the first operating state BZ1 with the lower stiffness Si. This allows the critical speed range, which would apply to the bearing-shaft assembly with higher stiffness S2, to be traversed without a vibration peak occurring, or with the vibration peak significantly reduced.

[0089] The bearing-shaft assembly can thus be driven through critical speed ranges through the targeted use of the different operating states BZ1 and BZ2, whereby the vibration maxima to be expected there are avoided.

[0090] In one embodiment, the bearing-shaft assembly is generally operated in the second operating state BZ2 for a predominant part of the operating time, i.e. with the clamping element 6 activated or subjected to high hydraulic pressure and with higher rigidity S2, and repeated brief deactivation and reactivation of the clamping element, i.e. brief switching to the first operating state BZ1 and switching back to the second operating state BZ2, ensures a relief, in particular thermal relief, of the bearing-shaft assembly.

[0091] In a variation not shown with a hollow shaft, the arrangement can also be reversed, i.e. the receiving element or the bearing is on the inside and the shaft is on the outside as seen from the axis of rotation.

[0092] Further aspects and embodiments according to the invention are also described below and can be claimed independently: a) Targeted clamping of sliding bushings with integrated rolling bearings in order to regulate the system stiffness and the resulting vibration amplitudes, with the aim of shifting natural frequencies and traversing them as required. b) The stiffness of rolling bearing systems is actively regulated with the help of clamping mechanisms in order to shift the natural frequencies of shaft-bearing systems in order to expand the usable speed range. c) For this purpose, sliding bushings are held in a non-critical position for the rolling bearings using clamping mechanisms, and the stiffness of the connection between the rolling bearing and the bearing shield is specifically regulated. This changes the system stiffness, the natural frequencies increase, and the vibration amplitudes in the previously given speed range decrease.The maximum speed of the clamped shaft-bearing system can be increased without damaging the rotating and stationary components. d) It is now possible to enter previously critical speed ranges and, depending on the system design, to continue running through them. Furthermore, depending on the design of the shaft-bearing system, it is possible to deactivate the clamping again after passing through the previous natural frequency range and continue running at a supercritical level. e) Brief increases in vibration amplitude when passing through or resetting the clamping mechanism can be made non-critical by damping or design measures. f) The clamping of the sliding bushing can be specifically influenced based on vibration amplitudes, vibration velocities, thermal and / or mechanical conditions in the system.g) Near the natural frequencies of shaft-bearing systems, vibration amplitudes increase continuously and, depending on the damping properties of the system, can reach very high values. High vibrations cause mechanical damage to rolling bearings, rotors, and other components. h) Electric motors, spindle units, and fast-rotating shaft-bearing systems are generally designed according to the locating / loose bearing principle in order to compensate for thermally and / or mechanically induced shaft misalignments. For this purpose, the rolling bearing(s) is / are installed in a sliding bush. This can compensate for thermally and / or mechanically induced shaft misalignments without destroying the rolling bearings due to excessive surface pressures. In order to realize the sliding function, loose bearing arrangements do not have high axial and radial rigidity due to the required sliding gap.If the sliding gap is bridged and a connection to the bearing shield is established, the axial and radial stiffness of the shaft-bearing system increases. At the same time, the vibration amplitudes can be reduced compared to a shaft-bearing system without clamping. This makes it possible to achieve higher speeds at the same vibration velocity level. i) By specifically clamping the sliding bushing, with a suitable design of the bearing system, natural frequencies present in conventional solutions can be passed through. After passing through the clamping force, the clamping can be released and the shaft-bearing system can continue to operate supercritically. Brief increases in vibration amplitude when passing through or resetting the clamping mechanism can be made non-critical by damping or design measures.j) The locking of the sliding bushing can be specifically controlled or regulated based on vibration amplitudes, vibration velocities, rotational speeds, thermal and / or mechanical conditions in the system.

[0093] Embodiment 1: Targeted, active clamping of sliding bushings with built-in rolling bearing units, whereby the stiffness of shaft-bearing systems is changed depending on the application so that critical natural frequencies can be shifted and / or passed through at low or non-critical amplitude values, as shown by way of example in Figure 1.

[0094] Embodiment 2: Targeted fixing of bearing units in sliding bushings according to or for embodiment 1, wherein one or more rolling bearings are installed in a sliding bushing which is fixed by means of mechanical (e.g. hydraulic, pneumatic, etc.) or electrical clamping mechanisms, as shown by way of example in Figure 2.

[0095] Embodiment 3: Mechanical or electrical clamping mechanisms according to or for embodiment 2, which create a force-locking connection between the sliding bush and the bearing shield, thereby increasing the axial and radial rigidity of the bearing system.

[0096] Embodiment 4: Mechanical or electrical clamping mechanisms according to embodiment 2, which are installed or mounted in the sliding bushing or in the bearing plate.

[0097] Embodiment 5: Mechanical or electrical clamping mechanisms according to embodiment 2, whereby these can be specifically activated and deactivated or controlled depending on one or more system-relevant input variables.

[0098] Embodiment 6: Targeted activation of the clamping mechanism according to embodiment 4, wherein the sliding bushing is clamped, thereby increasing the radial and axial stiffness of the shaft-bearing system, reducing vibration amplitudes, and allowing the radial natural frequency to be traversed, as it would be without clamping. After traversing, the clamping can be released or maintained, depending on the physical necessity and specified by higher-level control or regulating mechanisms. List of reference symbols

[0099] 1 shaft 2 bearings

[0100] 3 Rolling elements 4 Bearing inner ring

[0101] 5 Bearing outer ring 6 Clamping element

[0102] 7 Cavity 8 Receiving element (bearing shield)

[0103] 9 Speed ​​sensor 10 Temperature sensor

[0104] 11 Vibration sensor 12 Bearing

[0105] 13 rolling elements

[0106] 14 Bearing inner ring 15 Bearing outer ring

[0107] 17 Hydraulic line 22 Mounting block

[0108] 23 Sensor signal lines 24 Control unit

[0109] 25 Hydraulic unit 26 Control line A Rotation axis v,vl,v2,vmax Vibration speed n, no, ni, nz Speed ​​ns, n4 Speed ​​n A , n B critical speed

[0110] At intermediate speed interval t time BZ1 first operating state BZ2 second operating state MA resonance maximum on curve (1) MB resonance maximum on curve (2)

[0111] PI point on curve (1) at ni and v2

[0112] P2 point on curve (1) at n2 and v2

[0113] P3 Point on curve (2) at ni P4 Point on curve (2) at ns and v2

[0114] P5 point on curve (2) at n4 and v2

[0115] P6 point on curve (1) at ns

[0116] S, Si, S2Stiffness Ul, U2 Switching point

Claims

Patent claims 1. Bearing-shaft assembly comprising: a) at least one shaft (1) which is rotatable or rotating about an axis of rotation (A) and which is mounted in at least one bearing (2, 12), in particular arranged coaxially to the axis of rotation (A), b) at least one clamping element (6) for exerting a clamping effect or clamping force between the at least one bearing (2) and at least one receiving element (8), in particular a bearing plate, wherein the at least one bearing (2, 12) is arranged between the at least one receiving element (8) and the shaft (1), in particular coaxially to the axis of rotation (A), and / or for exerting a clamping effect or clamping force between the bearing (2) and the shaft (1), c) wherein the at least one clamping element (6), in particular by means of a control unit (24), is controllable or activated or activated,that by increasing the clamping effect or the clamping force, the rigidity of the bearing-shaft assembly can be or is increased and / or a resonance range and / or a natural frequency of the bearing-shaft assembly can be or is shifted., 2. Bearing-shaft assembly according to claim 1, wherein the bearing (2, 12) comprises a sliding bushing in the manner of a loose bearing and the or at least one clamping element (6) is integrated in the sliding bushing or is formed with the sliding bushing.

3. Bearing-shaft assembly according to claim 1 or claim 2, wherein at least one clamping element is a hydraulically or pneumatically actuated or activatable clamping element and / or wherein at least one clamping element is an electrically or electromechanically actuated or activatable clamping element, in particular a wedge clamping element or a clamping sleeve.

4. Bearing-shaft assembly according to one of the preceding claims, in which the at least one or each bearing (2, 12) comprises rolling elements, in particular balls (3, 13), which are held between a bearing inner ring (4, 14) and a bearing outer ring (5, 15), and / or in which at least two bearings (2 and 12) arranged one behind the other axially to the axis of rotation (A) are mounted.

5. Bearing-shaft assembly according to one of the preceding claims, in which at least one clamping element, in particular in a sleeve-shaped or annular section, has at least one cavity (or hollow space) (7), which is filled or can be filled with a hydraulic medium, in particular by means of a hydraulic unit (25) connected to the control unit (24) via a control line (26) and to the at least one cavity (7) via at least one hydraulic line (17), and can be subjected to a hydraulic pressure in the hydraulic medium, wherein preferably by the hydraulic pressure in the cavity (7), a region of the clamping element (6) lying between the cavity (7) and the bearing (2 or 12), in particular a membrane-like region, can be pressed or is pressed, in particular in the radial direction, against the bearing (2, 12) and / or the at least one receiving element (8),in particular after an initial expansion movement to overcome a radial play and subsequent contact with the bearing (2, 12), preferably its outer ring (5, 15), or the at least one receiving element (8) and due to the hydraulic pressure a clamping pressure or a, in particular radial, Clamping force of the clamping element (6) can or does exert on the bearings (2, 12) and thus the shaft (1).

6. Bearing-shaft assembly according to one of the preceding claims, wherein in a first operating state (BZ1) the clamping element (6) has a slight radial play relative to the bearings (2 and 12) or the at least one receiving element (8), in particular corresponding to a floating bearing, or exerts no or only a slight clamping force, so that a first stiffness (Si) and / or a lower first natural frequency or a first resonance maximum (MA) results at a first critical speed (HA), and in at least one second operating state (BZ2) the clamping element (6) exerts a higher clamping force than in the first operating state, so that a second stiffness (S2) results that is higher than the first stiffness (Si) and / or a second natural frequency that is higher than the first natural frequency, or a second resonance maximum (MB) that lies at a second critical speed (HB) that is higher than the first critical speed (HA),wherein preferably the control unit (24) switches or can switch between the operating states (BZ1 and BZ2) by controlling the clamping element (6) and adjusting its clamping force and thereby shifts or can shift the resonance range and / or the natural frequency of the bearing-shaft assembly.

7. Bearing-shaft assembly according to one of the preceding claims, a) in which the clamping element or the clamping force is or can be controlled or adjusted depending on at least one or more operating variables or operating parameters, wherein the operating variable or the operating parameter preferably comprises at least one or more of the following: (i) a vibration, preferably a vibration amplitude or a vibration velocity, in the bearing-shaft assembly or a coupled component, (ii) an operating temperature of the shaft and / or the at least one bearing (iii) the speed of the shaft (iv) a mechanical stress, and / or b) in which at least one sensor (9, 10, 11) or a combination of sensors (9, 10, 11) for detecting one or more of these operating variables or operating parameters, wherein the sensor(s) are preferably arranged in or on the bearing-shaft assembly, in particular (i) at least one vibration sensor (11), (ii) alternatively or additionally at least one temperature sensor (10), (iii) alternatively or additionally at least one speed sensor (9), (iv) alternatively or additionally, at least one mechanical stress sensor.

8. Bearing-shaft assembly according to claim 7 and claim 6, wherein the control unit switches between the operating states depending on one or more of the operating variables or operating parameters or on one or more of the sensor signals of one or more of the sensors, in particular when a critical threshold is reached.

9. Bearing-shaft assembly, in particular according to one of the preceding claims, characterized by a targeted, active clamping of sliding bushes with built-in rolling bearing units, wherein the rigidity of the bearing-shaft assembly depends on the application. gig is changed or can be changed in such a way that critical natural frequencies can be shifted and / or passed through at low or non-critical amplitude values, in particular by targeted fixing of the bearing units in the sliding bushes, wherein preferably one or more rolling bearings are installed in a sliding bush which is fixed with the aid of mechanical (e.g. hydraulic, pneumatic, etc.) or electrical clamping mechanisms, wherein preferably the clamping mechanisms produce a force-locking connection between the sliding bush and the bearing shield, whereby the axial and radial stiffness of the bearing system is increased and / or wherein preferably the clamping mechanisms are installed or attached in the sliding bush or in the bearing shield, wherein preferably the clamping mechanisms can be specifically activated and deactivated or controlled depending on one or more system-relevant input variables.

10. Electric motor connected to a bearing-shaft assembly according to one of the preceding claims.

11. Method for operating a bearing-shaft assembly according to one of the preceding claims, comprising the following steps: a) accelerating a rotatable shaft (1) of the bearing-shaft assembly; b) detecting or monitoring a vibration parameter of an undesired vibration of the bearing-shaft assembly, such as a vibration amplitude or vibration velocity; c) determining whether the vibration parameter reaches a critical threshold value (v2); d) upon reaching the critical threshold value, changing the stiffness of the bearing-shaft assembly and / or shifting the resonance range and / or a natural frequency of the bearing-shaft assembly, in particular by means of the at least one clamping element (6).

12. The method according to claim 11, wherein the acceleration of the shaft takes place in a first operating state (BZ1) with a first stiffness (Si) and / or a lower first natural frequency or a first resonance maximum (MA) at a first critical speed (UA) and, upon reaching the critical threshold value and in at least one second operating state (BZ2), switching is carried out with a second stiffness (S2) which is higher than the first stiffness (Si), and / or a second natural frequency which is higher than the first natural frequency, or a second resonance maximum (MB) which is at a second critical speed (HB) which is higher than the first critical speed (HA), wherein preferably upon further increase of the speed of the shaft in the second operating state (BZ2) upon again reaching the critical threshold value, switching is carried out again from the second operating state to the first operating state.

13. Method for operating a bearing-shaft assembly according to claim 6 or one of the claims dependent on claim 6, in which the bearing-shaft assembly is operated in the second operating state (BZ2) and by regularly switching to the first operating state (BZ1) a relief of the clamping element (6) and / or the bearing-shaft assembly is achieved.

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