FI118862B - Method for damping rotations of a rotating body and dynamic vibration damping - Google Patents

Description

118862

Method for damping rotations of a rotating body and dynamic vibration damping

The invention relates to a method for damping vibrations produced by a rotating body by means of a dynamic vibration damping device comprising a spring mounted on a rotating body and a mass mounted on a spring. The invention also relates to a dynamic vibration dampener.

All rotating devices vibrate. Most vibrations are harmless, but in some cases, vibration can cause serious problems such as shortening the life of the device, unexpected breakages, and increased noise levels. Vibration can also adversely affect the manufacturing process in which the rotating device is used. In particular, in paper machines and paper finishing equipment, vibration is a major problem. In paper and finishing machines, sources of vibration include rollers 15 and cylinders used in calenders, presses and coating machines, for example. These rollers and cylinders have high mass and rotational speed, which can lead to significant vibration problems. As the rotation speeds continue to increase, more vibrations will be generated. The problem of vibration of rollers and cylinders can be reduced by structural changes and by improving dimensional accuracy. However, this is not always possible or economically viable.

It is known that the vibration of a body can be damped by attaching to it a high-frequency tuned spring-mass system, or dynamic vibration dampener. When properly tuned, the body is attached the spring-mass system begins to oscillate at the same frequency but in the opposite phase to the object to be suppressed, and in optimum cases the oscillations can then be completely eliminated.

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Fl 101320 B discloses a method of damping vibration in a paper machine or paper finishing machine with a dynamic vibration damping device comprising a spring attached to a vibrating object and an additional weight suspended on the spring. The method measures the vibration frequencies of a continuously oscillating target with one or more oscillation sensors. The vibration sensor signals are • amplified by an amplifier and fed to a vibration analyzer [. *. Based on the measurement signals, the vibration analyzer1 determines the problematic oscillation frequency and, on the basis thereof, generates a control signal which is supplied to the control device. Based on the control signal, the control device changes the spring constant and / or the mass of the dynamic vibration damper so that the characteristic frequency of the dynamic vibrator becomes substantially the same as that of the vibrating object. F1 104208 B discloses tuning such an oscillator to a plurality of problem frequencies of varying magnitude, such that the tuning frequencies follow each other in a cyclic cycle. Fl 104209 B discloses a dynamic oscillator of the kind described above, with a number of additional weights that allow the attenuator to be tuned to a number of problematic excitation frequencies.

The dynamic vibration dampers 10 described in the aforementioned patents require at least one vibration transducer for measuring vibrations, an amplifier for amplifying a measurement signal, a measuring signal analyzer, and a control device for changing the characteristic frequency of the vibration dampener. Such equipment is complicated and expensive.

It is an object of the invention to provide an alternative method of damping vibrations by means of a dynamic vibration dampener.

The objects of the invention are achieved by a method and a dynamic vibration dampener, which are characterized in the independent claims. Certain preferred embodiments of the invention are set forth in the dependent claims.

·· • i j. In the method of the invention, the vibrations generated by a rotating body, such as a roll of a paper machine '•' f, are damped by a dynamic vibration dampener el ί. A dynamic vibration damping device is a device known per se, comprising a spring mounted on a rotating body and a mass mounted on a spring.

The dynamic attenuator has to be tuned to the new characteristic frequency each time the rotational speed of the 25 rotating bodies changes, because then the frequency of the vibrations produced by the body also changes. The method according to the invention provides The main idea is to adjust the dynamic attenuator to the appropriate characteristic frequency. '' · * ·. delle based on the rotation speed of the rotating body. In the method, first, an equivalence curve is formed between the rotational speed of the rotating body and the frequency of vibration generated by the rotation. When the part is in rotational motion during use, the current rotation speed of the part is determined. After this, the frequency of the vibration generated by the rotating body is determined by the rotation speed and the matching curve. Next, we determine the mass of the mass cap, or the spring constant of the spring, at which the characteristic of the dynamic damper becomes the same as the frequency of vibration of the rotating body. Finally, the characteristic frequency of the 3 118862 dynamic attenuator is tuned to the oscillation frequency of the rotating body.

In a preferred embodiment of the invention, the dynamic attenuator is tuned to the desired specific frequency by varying the mass of the mass or the spring constant 5 of the spring. Preferably, the spring constant of the spring is changed by displacing a mass body attached to the spring and / or moving the spring in the spring retainer.

In another preferred embodiment of the invention, the equivalence curve between the rotational speed of the rotating body and the frequency of the oscillation generated by the rotation is generated and stored during the installation of the dynamic vibration dampener 10, thereafter used to retune the dynamic vibration dampener. Preferably, the correspondence curve between the rotational speed of the rotating body and the frequency of the vibration generated by the rotation is formed by driving a so-called rotary body. the velocity ramp and the vibrations produced by the mit-15 at the same time. An equivalence curve can also be generated in conjunction with the use of a rotating body by measuring the vibrations generated during operation.

In a third preferred embodiment of the invention, the specific frequency of the dynamic damping device is tuned to the frequency of the oscillation of the rotating body as the rotation speed of the rotating body changes.

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The dynamic vibration dampener according to the invention for damping vibrations produced by a rotating body comprises a spring attached to a rotating body and a mass body attached to a spring. The damper is characterized by -: **] in that it further comprises means for determining the rotational speed of the rotating body, means for rotating the rotary body and generating rotation. . ·. means for generating a correlation curve of this oscillation frequency, ···. and determining means for tuning the characteristic frequency of the dynamic attenuator to the same frequency as the vibrations of the rotating body.

A preferred embodiment of the dynamic vibration damper according to the invention further comprises an actuator for moving the mass body and / or spring to change the distance between the mass body and the spring fastener and to control the operation of the actuator actuator.

118862 4

In another preferred embodiment of the dynamic vibration damper according to the invention, the mass body is designed to be mass changeable.

In a third preferred embodiment of the dynamic vibration damper according to the invention, the damper is provided with internal damping. Preferably, the internal damping is accomplished by forming a mass body of a closed shell portion and a liquid and / or granular material therein.

An advantage of the invention is that it is structurally simple, with low manufacturing costs, easy installation and low maintenance.

The invention will now be described in detail. Reference is made to the accompanying drawings, in which Figure 1 illustrates, by way of example, a schematic diagram of a dynamic vibration dampener used in the method of the invention.

Figure 1 shows, by way of example, a dynamic vibration dampener used in the method of the invention. The vibration damper comprises a spring 10 attached at its first end to a rigidly oscillating "rotating body 12 by means of fasteners 14. The spring may be in the form of a bar as shown in Fig. 1 · · · * 20 or may have another shape, e.g. It is only essential that the spring is a structural element for which a spring constant can be determined. In the example shown in Fig. 1, the rotating body is a roll of a papermaking machine, meaning a roll formed by a rotating roller and stationary roll bearing housings 13. The spring is secured to the bearing housing of the 25 rollers. There is a disk-like mass 16 near the other end of the spring, through which the spring passes through a central hole. The coupling between the mass body and the spring can be arranged by any suitable means. Actuator 1 is provided in connection with the mass body 8, by means of which the mass body can be moved in different positions along the length of the spring, whereby the characteristic frequency of the damper ·: **: 30 changes accordingly. The basic equation for the design of a dynamic damper follows the known formula: t ·: k / m = Ω, where 5 118862 k = spring constant of spring 10, m = mass of mass 16 and mass = angular velocity of vibrating body.

The function of the dynamic attenuator is based on tuning the characteristics of the attenuator-5 as closely as possible to the excitation frequency of the vibrating body. The dynamic attenuator only effectively attenuates the relatively narrow frequency range, so it is necessary to adjust the attenuator frequency to find the correct characteristic frequency. The spring constant k of the spring 10 can be determined computationally when the distance L between the mass pieces 16 and the spring clamp 14 is known. Thus, the specific frequency of the damper can be changed simply by moving the pulp 16 by means of the actuator 18 in the longitudinal direction of the spring 10, whereby the spring constant of the spring 10 changes as the distance L between the pulp 16 and the spring 10. In order to allow the mass body to move, it must be movably attached to the spring. When the specific frequency of the dynamic attenuator is tuned to the vibration frequency of the rotating body, the attenuator begins to vibrate at the same frequency but in a phase opposite to that of the rotating body. At the same time, the vibration of the rotating body is significantly damped and, in the optimum case, ceases completely.

In the method according to the invention, the change of the spring constant of the spring 10 can: ·. Alternatively, it may also be implemented by moving the spring through the clamp 14 in the longitudinal direction of the spring, whereby the distance *: between the pulp 16 and the clamp will change accordingly. In this preferred embodiment of the invention, the spring is movably secured to the fastener 14, whereby the mass piece 16 can be fixedly fixed to the spring 25.

• · · * * «; **. In the method according to the invention, the specific frequency of the dynamic attenuator can also be changed by decreasing or increasing the mass of the mass body 16. The spring constant of the spring 10 need not be changed at all, but may:!: Be constant. The attachment of the spring to the rotating body and the attachment of the mass body to the spring **: * '30 can then be performed in a fixed manner. The enlargement and reduction of the mass body can be accomplished, for example, by forming a mass body: · · · into a reservoir within which a desired amount of liquid, such as water, can be pumped. By changing the amount of liquid in the tank, the mass and mass of the pulp body as well! . * as a result, the characteristic frequency of the attenuator changes accordingly.

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Often, the problematic excitation frequency of an oscillating object changes as the object is used. In paper machines, for example, the rotational speeds of rollers and cylinders vary greatly in different situations, whereby the problematic vibration frequency also changes. Therefore, it must be possible to change the characteristic frequency of the dynamic attenuator accordingly.

In the method according to the invention, the specific frequency of the dynamic attenuator is adjusted based on the rotational speed of the rotating body 12. When installing a dynamic damper, vibration measurements are made on the rotating body to determine problematic excitation frequencies. In vibration measurements, the rotating device 10 drives a speed ramp, which results in a correlation curve between the rotation speed of the rotating body and the harmful vibration frequency caused by the rotation. An equivalence curve can also be generated in conjunction with the use of a rotating body by performing vibration measurements of the body during operation. In this case, no separate speed ramp drive is required. With the aid of the matching curve, the frequency of vibration of the easily rotating body can be further determined as the rotational speed changes. Generally, the most harmful frequency is the rotation speed of the directly rotating body, or some multiple of it. Other possible onset frequencies are the resonant frequencies of the rotating bodies, which may wake up at a certain rotational speed, the so-called. problem-20 frequencies due to tooth grinding and problem frequencies dependent on fan and pump blade numbers.

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. The equivalence curve resulting from the vibration measurements is a unique curve, ** y, which generally remains substantially constant throughout the life of the rotating body, unless structural changes are made to the rotating body. This • * ·: · γ 25 allows you to determine the equivalence curve only once for a rotating body, after which this equilibrium curve can be used to control a dynamic · · · suppressor in principle for an unlimited time. The correspondence curve is stored in the damper control unit 20 which controls the pulp 16: the actuator 18.

In the method of the invention, the problem frequencies of the rotating body can also be determined by the so-called. impact test. The result of the impact test is the •: ·: oscillation spectrum of the song, from which the problematic frequencies are distinguished as "peaks".

When a rotating body, such as a paper machine roller, is in use, it rotates at a certain rotation speed. In the method according to the invention, the respective rotational speed of the rotating body is first determined. For determining the rotational speed 118862 7, the damper may have its own measuring apparatus (not shown). If the rotational speed information is available without separate measurement, for example through systems controlling and / or monitoring the operation of the device, this information can of course be used. This may be the case, for example, in paper machines, where the speeds of rotation of the individual rollers 5 and the cylinders are generally obtainable from the control room of the machine. The determined rotation speed information is transmitted to the dynamic damper control unit 20, where the rotation speed and the matching curve determine the vibration frequency of the rotating device. When the oscillation frequency is known, the control unit determines for the spring constant of the spring 10 the value at which the characteristic frequency of the dynamic dampener becomes equal to the problematic oscillation frequency of the rotating device. The control unit then gives the actuator 18 a control command to change the distance between the pulp 16 and the spring retainer 14 so that the spring constant of the spring changes to the desired value. The change of the distance L can be accomplished either by moving the mass piece attached to the spring or by moving the spring through the fastener 15 14. When the distance L is adjusted to fit, the damper will start to operate as intended. The above procedure is repeated as the rotation speed of the body changes.

In a preferred embodiment of the method according to the invention, the specific frequency of the dynamic attenuator is tuned to the desired value by reducing or increasing the mass of the pulp 16. In this embodiment, the pulp body comprises a fluid-tight container and a pump for pumping fluid into or out of the container. With the help of a pump, the amount of liquid in the tank and thus the mass -. * ·. ·. the mass of the body is adjusted to obtain the desired characteristic frequency for the dynamic attenuator.

In another preferred embodiment of the method of the invention, the dynamic attenuator is further provided with internal attenuation. The provision of internal attenuation provides the advantage that the attenuator is able to attenuate a wider frequency range. In this case, the attenuator does not need to be tuned as needed. . ·. dipped at a specific program frequency, which facilitates control of the attenuator. Interior ··. 30 attenuation can be accomplished in many different ways. One way of performing the internal * * damping is to form a mass body of a solid chamber containing a liquid such as water or oil or granular material *: ** such as sand or metal spheres. When a mass body is subjected to vibrating motion in a damping condition, frictional forces are created between particles of liquid or granular material within the shell to absorb vibration energy. Part of the vibration energy is then converted into heat energy by frictional forces.

Some preferred embodiments of the method and apparatus of the invention have been described above. The method and dynamic vibration dampers of the invention are particularly well suited for use in paper and finishing machines and other similar solutions comprising rotating rollers and cylinders. Other potential applications of the invention include, for example, wind turbines, where the invention can be used to dampen vibrations generated by the rotor and gearboxes. The method is also suitable for use in buildings, for example, to dampen vibrations generated by 10 pipelines. Vibrations also almost always produce noise. Thus, the method of the invention can also be used as a noise control method. The invention is not limited to the solutions just described, but the inventive idea can be applied in a variety of ways within the scope of the claims.

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Claims (16)

118862 9 A method for damping vibrations produced by a rotating body (12) by means of a dynamic vibration damping device comprising a spring (10) attached to a rotary body and a mass body (16) attached to a spring, characterized by: frequency, - determining the rotational speed of the rotating body (12), - determining the frequency of the oscillation generated by the rotating body (12) by means of a rotational speed and a matching curve, and - tuning the characteristic frequency of the dynamic attenuator to Method according to claim 1, characterized in that the characteristic frequency of the dynamic damping device is tuned to the frequency of vibration of the rotating body (12) by changing the spring constant of the spring (10). Method according to Claim 2, characterized in that the spring (10) is fixed to the rotatable body (12) by means of a fastener (14) and the spring constant of the spring (10) is changed by displacing the mass body (16) and / or moving the spring in the fastener (14). ·· • · • »·. 20 A method according to claim 1, characterized in that the characteristic frequency of the dynamic Ϊ attenuator is tuned to the frequency of the vibration of the rotating body (12) by changing the mass of the mass body (16). • · · * «· • M ♦: 5. Method according to one of Claims 1 to 4, characterized in that. ** ·. said correlation curve between the speed of rotation of the rotating body (12) and the frequency of oscillation generated by the rotation is generated and recorded during the installation of the dy-os oscillator, followed by this I !! the equivalence curve is used to tune the dynamic oscillator * "'* to the desired characteristic frequency for subsequent use of the rotating device. ·· * • · • · The method according to claim 5, characterized in that the corresponding · ·. A rotation curve 30 is formed between the rotation speed of the rotating body (12) and the frequency of oscillation produced by the rotation by driving a so-called rotating body. speed ramp and measuring the vibrations that occur simultaneously. 10 118862 Method according to Claim 5, characterized in that a curve of correspondence between the rotation speed of the rotating body (12) and the frequency of the vibration produced by the rotation is formed in connection with the use of the rotating body by measuring the vibrations generated during use. Method according to one of Claims 1 to 7, characterized in that the rotation speed of the rotating body (12) is determined by a measuring apparatus in a dynamic vibration dampener. Method according to one of Claims 1 to 8, characterized in that the characteristic frequency of the dynamic attenuator is tuned to the frequency of vibration of the rotating body as the rotational speed of the rotating body (12) changes. Method according to one of Claims 1 to 9, characterized in that the method is used to dampen the vibrations of the rolls of a paper machine and / or a finishing machine. Dynamic vibration dampener for damping vibrations produced by a rotary body (12), comprising a spring (10) attached to a rotary body and a mass body (16) attached to a spring, further comprising: means for rotating the rotary body (12). means for generating a correlation curve between rotation speed and rotation of the rotating body: • · v .: means for determining a characteristic of a dynamic attenuator by means of a rotational speed and an equivalence curve and: means for adjusting a characteristic of a dynamic attenuator at the same frequency as the vibrations. Dynamic vibration damper according to claim 11, characterized in that it further comprises a t-actuator (18) for moving the mass body (16) and / or the spring (10) C. ' : to change the distance between the mass block and the spring clamp (14), and. ·· *. A control unit (20) for controlling the operation of the actuator (18). • ·· # Dynamic vibration damper according to claim 11, characterized in that the mass body (18) is designed to be mass changeable. · * · * »* • · • · u 118862 Dynamic vibration dampener according to one of Claims 11 to 13, characterized in that it is provided with internal damping. Dynamic vibration damper according to Claim 14, characterized in that the pulp body (16) consists of a closed shell part and a liquid and / or granular material therein. Dynamic vibration damper according to Claim 15, characterized in that liquid, sand and / or metal balls are contained within the pulp body. * · • · • M • · • · · I »» • · m • · · ft · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · • 1 • · ··· • t · • · · f1 · ♦ 2 • · • · ft · · · · · · · · · 1 P 2 · • · · 1 P ft 12 1 1 8862