The invention relates to a device for damping oscillations of a rotating construction element, in particular an oscillation absorber.
The expression xe2x80x9cDevice for damping oscillationsxe2x80x9d is to be understood in the broadest sense. It can be a matter here of so-called oscillation dampers, vibration damping arrangements or combined arrangements between oscillation damper and vibration damper. By oscillation damper there is meant here a device which serves for the decomposition of occurring vibrations, especially on rotating construction components, and not for the damping of oscillations in the torque transfer between two components in the drive string. A damper, therefore, does not participate primarily in the torque transmission during the entire operation from a drive side to an off-drive side. In a vibration damping arrangement it is a matter as a rule of an elastic coupling which is arranged between two construction components, for example a combustion power machine and a gear. Such couplings do not serve to transfer torsional oscillations from the rotor to the remaining drive string. Such an elastic coupling is disclosed in the application DE PS 28 48 748. In DE 197 28 894 there is disclosed a combined oscillation eradicator-damper arrangement. The spring arrangements provided there between the two elementsxe2x80x94primary mass and secondary massxe2x80x94serve for the carrying along of the secondary mass during the starting phase and the acceleration phases. Otherwise there occurs substantially no torque transmission.
Devices for the damping of oscillations (or vibrations) are formed in such manner that the critical turning rate of the total mass system lies sufficiently far below the operating range. There, in the passing-through of the critical turning rate no great amplitudes, and no great torsion moments in the individual elements are to arise.
Essential elements of an oscillation suppressor or of a damper are a damping arrangement as well as a spring arrangement. The damping arrangement comprises chambers which are connected in conducive connection via channels of defined width. There, during operation, a damping agent is displaced from the one chamber via the channel into the adjacent chamber. The spring arrangement comprises a plurality of springs, which are mounted on a circuit coaxial to the damper or suppressor axis.
In practice it is proved that torsional vibrations are not damped as strongly as is desired. Resonance vibrations arise. These can be very disadvantageous, In the printing industry, for example, they can lead to so-called register inaccuracies.
Underlying the invention is the problem of giving a device for the damping of oscillations, in particular a vibration eradicator, in which all vibrations (or oscillations) are perfectly damped or eradicated in such manner that no undesired resonances arise which impair the work result.
This problem is solved by features of the independent claims.
An essential insight lies in that in known devices for vibration damping, in particular in oscillation dampers, the force-path diagram or the spring characteristic curve has no absolutely linear course, but presents at least one jump point or a free-floating course. This means that in the allocation of load and the deformation of the spring in the load change in the first case a greater force brings about no deformation, while in the second case, without force action, a certain expansion of the spring or a contraction would be possible. The inventors have first recognized that this jump point or the free-floating are (sic) responsible for undesired resonances. Then, they have drawn from this fact the conclusion that the region or zone of the jump place or of the free floating must be avoided in operation, and that, accordingly, the work must be done either only in the so-called compression zone or in the so-called expansion zone, in which the compression can be characterized essentially by thrust stress and reduction of the spring length and the expansion zone can be characterized by tension load and increase of the spring length. This means, in other words, that the spring device(s) is to be correspondingly pre-tensioned in order to achieve shortening or lengthening of the spring length for the compensation of the relative movements of the individual masses to one another in peripheral direction to one another, so that the transition range between thrust and pull is not affected at all during suspension of a pretension. There, for constructive reasons it is to be preferred to pretension spring elements in the form of pressure springs.
According to the invention it is provided to design a device for oscillation damping with a primary mass and with a secondary mass torsionally coupleable, at least indirectly, with the rotating construction element, in which system primary mass and secondary mass are coupleable in a damping and spring coupling, and means for the realization of the spring coupling are provided in the form of spring arrangements, in such manner that the spring arrangements comprise at least two spring elements which are arranged, as viewed in peripheral direction of the device, pretensioned in succession between primary mass and secondary mass, and the two spring elements of a spring arrangement are supported against one another by support of the primary mass with respect to the secondary mass. Therewith from the characteristic curves of the two spring elements there is developed a characteristic curve for the total spring arrangement which is free from jump points or floating passages.
The pretension there is to be chosen in such manner that on full spring deflection of the first spring elements, i.e. reduction of the spring length under thrust load, the other, second spring element of the spring arrangement, which undergoes an unburdening, still has a pretension of a certain magnitude. In the other casexe2x80x94full spring deflection with lengthening of the spring length in peripheral direction under pull loadxe2x80x94the other, second spring element, which is stressed for pressure is still pretensioned. Thereby it is achieved that on alternating load which is characterized by a change of the turning direction of secondary mass with respect to primary mass, only one spring element of the spring arrangement continues to be pretensioned, while the other, second spring element is unburdened and the pretension is in part suspended, in which case an increase of the pretension is to be achieved for both spring elements of a spring arrangement only by the same type of load. A compensation therefore of the relative movements arising between the two masses is to be avoided on only one spring element by change of the stress of one spring element.
Primary mass and/or secondary mass are preferably executed as disk-form elements, in which context primary mass and/or secondary mass comprise either a one disk-form element or two disk-form elements. In the latter case, for example, the element of the device functioning as secondary mass can comprise for the oscillation damping two disk-form elements, in which case the disk-form element of the primary mass is arranged between these two. The converse case is likewise conceivable.
The term xe2x80x9cdisk-form elementsxe2x80x9d is to be understood as each disk-form element operates as a single component. Each disk-form element can, in turn, itself be composed of a plurality of disk-form components. As a rule the term primary mass is used in the case of oscillation dampers for the mass parts coupleable at least indirectly torsionally with the rotating component, and the term secondary mass is used in this case for the freely oscillating mass part. In the case of oscillation damping arrangements there is understood under the designation xe2x80x9cprimary massxe2x80x9d as a rule the mass part torsionally coupled with the drive side, while as secondary mass there is designated the mass part connectable torsionally with the off-drive side.
In the constructive execution for the realization of the arrangement of the spring arrangements the primary mass comprises first recesses running in peripheral direction. The secondary mass comprises second recesses essentially complementary to the first recesses on the primary mass with respect to their spacing and size, in which the installation position in the nonfunctioning state (no occurrence of oscillations), the so-called middle position or zero-turning between primary mass and secondary mass is characterized in that the recesses on the primary mass and of the secondary mass overlap one another in such manner that the wall zones of the secondary mass supporting the spring elements in peripheral direction are arranged about in the middle of the recess of the primary mass. In other words, the secondary mass, with identical formation of the recesses in respect to their recess in peripheral direction can be arranged offset by half the extent of the recess of the primary mass in peripheral direction. Through this arrangement in the so-called middle position, i.e. in installation position without exercise of function, the zone formed theoretically by the recesses on the primary mass are subdivided in two receiving zones for the spring elements, essentially of equal size in peripheral direction. These two spring elements form in common the spring arrangement according to the invention. The spring elements are supported there in peripheral direction on the outer walls of the recess of the primary mass and in each case by the wall areas formed by the secondary mass. To each of the spring elements there is allocated on the spring ends in each case a guide body on which the two massesxe2x80x94primary mass and secondary massxe2x80x94engage tangentially in the zone of the receiving zones. The spring elements themselves are installed with pretension, the pretension being selected in such manner that on complete spring deflection of a spring element of a spring arrangement the other spring element still has a pretension of a certain magnitude.
As spring elements there can be pulled tension springs or pressure springs. Preferably, however, pressure springs as used, whereby a space-saving execution of the device can be achieved.
The individual guide elements or guide bodies which are designated also as spring xe2x80x9cpotxe2x80x9d, can be formed differentially. Preferably, however, there are used elements laid out alike and executed alike for a given device.
Further, preferably between the primary and the secondary mass means are provided for the damping of longitudinal and/or rotary oscillations, which counteract a relative movement of the primary mass with respect to the secondary mass and transform the work performed by the relative movement of the primary mass with respect to the secondary mass by the thrust forces, for example, into heat. Preferably the damping occurs hydraulically. For this purpose the means for the damping between the primary and the secondary mass comprise a hydraulic fluid, i.e. an incompressible fluid. The use of other media, for example of an elastic material, is likewise conceivable. The damping medium can be provided there in separately, essentially closed-off chambers that are provided with the provision of corresponding recesses complementary to one another, or that can be arranged in the zone of the spring devices. It is likewise thinkable to provide the damping medium in the zone of an arrangement for the realization of a twist angle limitation. Also possible is a complete filling or discharge of the interspace between primary and secondary mass. The supplying with hydraulic fluid as damping medium can occur, for one thing, from outside, during the operation or by exchange via a hydraulic fluid supplying system. Further, the supplying can occur once by means of a separating operating medium supply device, i.e. by a damping filling of its own or else directly from the aggregate to be damped over a corresponding supply line. In this connection there is also thinkable the formation of a circulation which makes it possible to maintain the hydraulic fluid always at a constant temperature.
In the constructive execution the primary mass, which is preferably executed as a disk-form element, is coupleable at least indirectly torsionally (twistproof) with the rotating component in the drive string on which the there appear longitudinal and/or rotary oscillations which are to be compensated. To the primary mass there is allocated the secondary mass, which is allocated to the primary mass without coupling, or else is connected with the drive-side part. The transfer of the longitudinal and/or rotary oscillations or the supporting of these on the secondary mass occurs by means of the spring arrangement. The individual spring arrangements are arranged there preferably over a certain defined diameter in peripheral direction in corresponding recesses on the primary mass and are supported always on the secondary mass. The spacing in peripheral direction is preferably constant. In regard to the concrete constructive execution of the spring support reference can be made to the statements made in this regard corresponding to the publications DE-OS 363-35 043 and DE 39 16 575. The disclosure content of these publications in respect to the possibilities of supporting a spring between two elements is herewith included in its full volume in the disclosure content of the application.
Over the spring arrangements the oscillations on relative movements of the primary mass with respect to the secondary mass are compensated by the latter. In use in the oscillation damperxe2x80x94i.e. in the case of nonoccurrence of longitudinal and/or rotary oscillations on the drive unit on which the drive device for oscillation damping is mountedxe2x80x94there occurs a rotation of primary and secondary masses with the same velocity. This means that no relative movement takes place between the two. The spring devices provided between the two elementsxe2x80x94primary mass and secondary massxe2x80x94serve then merely during the starting phase and the acceleration phases for the carrying-along of the secondary masses; otherwise no torque transfer whatsoever occurs over these. In the event of occurrence of longitudinal and/or rotary oscillations on the rotating construction component, these are led into the primary mass. Over the spring devices there occurs a-transfer to the secondary mass in consequence of the relative movements between the primary and the secondary masses. The secondary mass is to be laid out there in respect to its inertia in such manner that it supports a certain measure of oscillations without problems. The layout occurs by corresponding establishment of the moment of inertia 1.
The weakening of the occurring relative movement takes place over corresponding means, preferably hydraulic ones. In this case in the region of the pressure springs or of a stop for the limitation of the twisting angle, chambers are provided which are fillable with a hydraulic fluid. This fluid on occurrence of relative movement is displaced between primary mass and secondary mass, but in the process it presents a resistance.
The same principle is usable also in oscillation damping arrangements, i.e. in arrangements for torque transfer with integrated damping. These, too, comprise as a rule a primary mass and a secondary mass, which are coupleable in a corresponding manner over spring arrangements.
For the exclusion of further resonance sources there are conceivable preferably the following measures:
Reduction of the frictional damping by corresponding design and layout of the spring pots or the axial guidance of the spring pots;
pinpointed adjustability of the shear damping by layout of the axial and/or radial bearing of the individual elementsxe2x80x94primary mass and/or secondary mass. For the reduction of the frictional damping on relative movement of the secondary mass with respect to the primary mass, the spring pot on the secondary mass is guided axially in such manner that this pot on relative movement with respect to the primary mass undergoes no additional movement relatively to the secondary mass. There the axial guidance can occur on the secondary mass, for example, over correspondingly formed sheet metal plates or set-offs. In the simplest case this effect, however, can also occur by use of two guide elements of different width for one spring element, in which case the spring element exposed to relative movement is executed more narrowly in axial direction.