FI121752B - Apparatus and method for controlling the runnability of a fiber web handling nip - Google Patents

Description

APPARATUS AND METHOD FOR MANAGING THE FIBERS OF THE FIBER HANDLING NIP

FIELD OF THE INVENTION

The invention relates to controlling the runnability of a fiber web handling nip. In particular, but not exclusively, the invention relates to damping the nip vibration of a fiber web machine.

BACKGROUND OF THE INVENTION

Vibration in the nipples of a fiber web machine impairs the runnability of the paper machine. For example, in a calender, nip vibration causes the rolls and / or belts to compress the fibrous web and / or the web of fibrous web to be modified. Transformation is manifested in the form of transverse stripes visible on the surface of the rolls and / or the belt and / or the fibrous web.

Nipple vibration is inherently unstable and self-excited. Vibration of the fibrous web processing element such as the roll surface or belt surface or webs in the nip acts as an additional excitation when the surface or web of the fibrous web processing member re-enters another nip of the same fibrous web processing device, e.g. In the case of a coating of a fibrous web treatment element, such as a roll coating, the re-entry of the modified coating into the same nip may serve as an additional excitation.

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The shaping described above occurs at the characteristic frequencies of a fibrous web processing device such as a calender roll, because at these frequencies the oscillation sensitivity is at its highest.

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The vibration sensitivity of the calender roll may have been influenced by developing new roll coatings and preventing synchronization between the roll rotation frequencies and the roll characteristic. Efforts have been made to prevent synchronization with 0X1 by changing the speed of the calendar or by affecting the characteristic frequencies of the calender rolls 2. The characteristic frequencies can be changed e.g. by adjusting the rigidity of the roller supports and adjusting the nipple cover.

Attenuation has been used to prevent roll vibration. The damping has been accomplished with 5 different mass suppressors which have been designed to influence the specific frequency of the oscillation system. Adaptive dampers have also been made whose specific frequency can be adjusted to changing conditions.

EP1275776A1 discloses a calender in which the elastic roll roll 10 is displaced laterally with respect to the compression plane of the roll set.

FI117566B discloses a method of changing the specific frequency of a roll supported by a hydraulic actuator by varying the fluid volume of the hydraulic system by at least 5% of the total fluid volume of the hydraulic system.

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SUMMARY

According to a first aspect of the invention, there is provided an apparatus for controlling the runnability of a nip formed between a first roll and a second fibrous web treatment member, which is a roll or belt, and a first roll supported on its ends by shafts. The apparatus comprises: - a hydraulic actuator, such as a hydraulic cylinder, adapted to provide an external hydraulic damping force opposite to the motion velocity of the anchor point at a first roll support point of the roller at ≤ 25, c \ j and i g - a hydraulic pulse generator

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for adjusting the frequency of the external hydraulically generated damping force 30 to influence the travel speed in the opposite phase.

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According to another aspect of the invention there is provided an apparatus for controlling the runnability of a nip formed between a first roll and a second fibrous web treatment element, which is a roll or belt, and the first roll being supported by bearings from the axes at its ends. The apparatus comprises: - a hydraulic actuator, such as a hydraulic cylinder, adapted to provide an external hydraulic damping force opposite to the speed of movement of the anchor point at the support point of the first roller, and - stage.

According to some embodiments, the apparatus comprises: - a nip oscillator 15 motion velocity sensor arranged at a first roll support point; coupled to a hydraulic actuator pressure line to adjust the frequency of the external hydraulically generated damping force to affect the movement velocity in the opposite phase.

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Preferably, the apparatus comprises a hydraulic pulse generator coupled to the i g hydraulic actuator for controlling the frequency and / or the amplitude of the external hydraulically generated damping force under pressure.

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in a step opposite to the speed of rotation, comprises a rotatably adjustable rotary valve spindle 30 and valve outlets which, when rotating the valve spindle o, close and open to adjust the frequency of the damping force.

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Preferably, the hydraulic cylinder producing the damping force is the same hydraulic cylinder adapted to form the nip nip pressure.

Preferably, the apparatus comprises a throttling of the outputs 5 of the hydraulic pulse generator or a hydraulic fluid line outgoing from said outputs to control the amplitude of the damping force.

Preferably, the apparatus comprises a piezo-actuated hydraulic device coupled to the hydraulic actuator for pressure change to vary the frequency and / or amplitude of the external hydraulically generated damping force.

Preferably, the apparatus comprises a measuring sensor suitable for measuring the velocity of the vibration movement, which is attached to a support point of the first roll, preferably the apparatus comprises an accelerometer mounted on a bearing housing.

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Preferably, the apparatus comprises a phase angle sensor suitable for determining the phase angle of rotation of the first roll, preferably a pulse sensor mounted on the end of the first roll.

Preferably, the apparatus comprises an external damping force measurement comprising a pressure sensor for measuring cylinder pressure or a force transducer for measuring the force exerted on the support point of a first roll or a strain gauge for measuring the strain of the support structure.

According to a third aspect of the invention, the method is implemented in a nip

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to control the runnability formed by a nip formed between the first roll and the second fibrous web treatment element, which is a roll or belt, and the first roll is supported x from its axes through the bearing housings.

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The method comprises:

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30 - providing an external damping force opposite to the vibration motion of the anchorage point at the support point of the first roll with a hydraulic actuator o such as a hydraulic cylinder;

According to some embodiments, the method: - measures nip vibration motion from the first roll support point, - measures the phase angle of rotation of the first roll, - produces an external damping force, with the hydraulic pulse generator connected to the pressure line, the frequency of the external hydraulically produced damping force to influence the movement velocity in the opposite phase.

15

Preferably, the external damping force is actively generated by measuring the motion amplitude of the first roll support point and adjusting the damping force amplitude to maximize damping power.

Preferably, the frequency of the external hydraulically generated damping force is controlled by varying the speed of rotation of the hydraulic pulse generator valve spindle, which hydraulic rotary generator comprises a rotatable valve valve spindle closing and opening.

Preferably, the amplitude of the external hydraulically generated damping force is adjusted by changing the throttling of the outputs comprised in the hydraulic pulse generator, or i g of the throttling of the line leading to the tank from said outputs.

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Preferably, to measure the external hydraulically produced damping force, the pressure of the hydraulic cylinder is measured, or the force exerted on the support point of the first roll of the hydraulic cylinder, or the first roll is measured.

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extension of the support structure.

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Preferably, one frequency component of the damping force is adjusted at a time.

Preferably, the measurements for damping force adjustment are made by averaging the speed, phase angle, and force measurements of the multiple components of the roll rotation frequency 5 until they are sufficiently varied.

Preferably, the damping power is maximized by an optimization algorithm using the damping force phase angle and amplitude, which damping power is the product of damping force and vibration motion. Preferably, the Newtonian iteration or gradient search algorithm is used as the optimization algorithm.

According to some preferred embodiments, the method further modifies the frequency and / or amplitude of the damping force produced by the hydraulic actuator by means of a piezo actuator arranged in pressure communication with the hydraulic actuator.

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Various embodiments of the present invention will be described or described only in connection with some or some aspects of the invention. One skilled in the art will appreciate that any embodiment of an aspect of the invention may be applied to the same and other aspects of the invention, alone or in combination with other embodiments.

BRIEF PRESENTATION OF THE PATTERNS

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: δ 25

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Fig. 1 is a side view of a two-roll calender; Fig. 2 schematically shows the upper roll of Fig. 1 as a vibrator; Fig. 3 schematically shows cross-sections of the nip rolls of Fig. 1;

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Figures 4 and 5 schematically show some arrangements for suppressing the nip vibration of the calendar 30 of Figure 1; Fig. 6 is a schematic cross-sectional view of a hydraulic pulse generator C '; and Fig. 7 is a longitudinal sectional view of the pulse generator of Fig. 6.

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DETAILED EXPLANATION

In the following description, like reference numerals refer to like parts. It is to be noted that the figures shown are not to scale in their entirety, and that they serve merely the purpose of illustrating embodiments of the invention.

Figure 1 shows a calendar 1 with lower roll 2 and upper roll 3 forming a nip N1 calendering the fibrous web W between them. Supporting and loading arms 7, which are pivotable about pivots 6, are mounted on the body 5 of the calender 1, to which the lower roll 2 is rotatably supported from its axes at both ends by means of bearing housings 4. The lower roller 2 can be moved on the support and load arms 7 supported to close and open the nip N1 and to load the lower roller 2 15 against the upper roller 3 above it. The upper roll 3 is rotatably supported from its shafts at both ends through bearing housings 8 to support members 9 rigidly attached to the frame 5. During calender 1 travel, the lower and upper rolls are in nip contact, whereby the derived fibrous web W between the nip N1 is calendered. Mounted on the body 5 of the calender 1 are hydraulic actuators 10, 20 which support and move the lower roller 2 on the support and load arms 7.

The hydraulic actuator may be a hydraulic cylinder 10. The hydraulic actuator may act on the bearing housing or, for example, the bearing and loading arms carrying and loading the roller. In Figure 1, the piston rod 11 of the cylinder 10 0 25 acts on the bearing housing 4 and may be secured to the bearing and loading arm 7 or bearing housing 4 in a manner that permits movement of the bearing and bearing 7. The load on the lower roller 2 can be adjusted

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x by varying the pressure p of the hydraulic fluid in the cylinder part 12. Each hydraulic cylinder 10 may be connected to its own separate hydraulic circuit, whereby the load on the cylinders 10 may be independently adjusted.

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If, during run of the calender 1, the rotation frequency of one of the rolls or its multiple coincides with or close to the characteristic frequency of the calender 1, harmful oscillations occur. In order to limit the oscillations at the critical point of the nip N1, where the oscillation is at its most detrimental to the processing of the fibrous web, the form of the oscillation is reduced. In this case, vibration may still occur in the bearing housing of the roller participating in the nip. Preferably, the bearing support of the 5 rolls participating in nip N1 can be made more flexible. The flexible bearing support can be implemented by installing a flexible material such as rubber or polymer material in connection with the support. Flexible support can absorb kinetic energy and vibration.

Figure 2 schematically shows the calender 1 and top roll 3 of Figure 1 as an oscillation system in which the mass x, oscillating at speed x is exerted by an external force F. In Figure 2, the direction of the external force F is downward and the direction x is upward. To dampen the oscillation, an external force F is applied in the opposite direction to the motion speed x.

15 In the oscillation system 1, the struts 3 'of mass m have a spring constant k and a damping c.

The internal damping force Fc of the vibration system is the product of the system damping c and the traveling speed x according to the following equation:

Fc = c x (1) 20

As an oscillation system of Figure 2, the calender structure 1 of Figure 1 is illustrated in which roller 3 rotating at rotational frequency T is supported at each end by a flexible support 3 '. The flexible support 3 'comprises, for example, the support o of the roll 3 through the bearing housing 8 to the body 5,9 of the calender 1. In the example of Fig. 2, the elastic strut ^ 25 3 'has a spring constant k and a damping c, and the roll 3 has an oscillating mass m. The elastic struts at different ends of the roll 3 do not necessarily have to be the same;

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Figure 3 shows schematically the nip rolls of the calender 1 of Figure 1

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λ 30 cross-sections and, by way of example, the geometry 3a of the cross-section of roll 3.

O) o The roll 3 of the calender 1 and the roll 2 below it form a nip N1. The roll 3 has a wavy profile 3a. As the roll 3 is rotated, the compression effect exerted by the roll 3 on the nip N1 (in the direction Θ = 180 °) varies because the radius value of the 9 roll 3 in the direction of the NIP varies with the angle of rotation Θ of the roll 3. At a phase angle Θ = 180 ° of roll 3, the radius of roll 2 in the direction of nip N is r. In the example of Figure 3, during a single rotation of the roll 3, the value of the roll radius r changes from ascending to descending seven times, resulting in a sevenfold oscillation frequency f relative to rotation fi due to the circular profile 3 'of roll 3. For example, roller 3 may have a 44-wave circular profile 3a, which when running the process at 1200m / min (20m / s) with 700mm diameter roller 3, the roller rotation frequency fi becomes 9Hz and the oscillation frequency f can be 44 times 9Hz or about 400. Hz. 10 Naturally, other variables also affect the vibration frequency of the nip, such as the circular profile of the second nip roll 2 and the web to be calendered in the nip. Typically, the oscillation at nip N1 is synchronized to a certain frequency. soft coatings. Similarly, oscillation and oscillation synchronization can also occur in oscillation systems formed by more than 15 rolls, but for the sake of simplicity of presentation, a double roll calender is used.

The damping power P at a given point in the structure is at its peak when, at this point, the product of the oscillation velocity x and the external damping force F reaches its minimum, P = work / cycle by damping force F, cycle time:

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P = f F x dt (2) 0

The damping power P is not maximized by the maximum external damping force F,

? but too large a damping force F limits the motion amplitude. With damping force F

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™ is thus a certain optimum of the maximum damping power P of the vibration system

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£ The damping external force F is applied as a function of time F (t). When exerting a rotating roll in Section 3, the external force F is a function of the oscillation frequency f and the phase angle Θ of the oscillation: o ° 30 F = F (t) = F (f, 0) (3) 10 The oscillation frequency f can be measured from the rotating roll 3, for example by means of an accelerometer 15 attached to the bearing housing 8 of the roll 3, and the harmful vibration frequency f is known, for example, as the barring frequency. The phase angle Θ 5 of the roll 3 rotation can be measured by a phase angle sensor 16, such as a pulse sensor, suitable for determining the phase angle of the roll 3.

When it is desired to maximize the damping power P, the amplitude and phase angle of the external damping force are adjusted such that the aforementioned damping power is maximized by 10 (term P minimum).

F (t) = A sin (ujt + Θ) (4)

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P (A, Θ) = / F (t) X dt (5) 0 A0pt, 0 opt [V δ, ε = $ P (A0pt, Θ opt) * · P (Aopt δ j 0 opt + ε)] ( 6) 15 -F (f, 0) x = cx (7)

The external damping force F of the calender 1 is actively produced. The motion amplitude of the roll 3 support point is measured and the damping force F is adjusted so that the damping power P reaches its maximum.

20

The external damping force F is applied to the support point of the roll 3, such as the bearing housing 8, by an actuator capable of generating significant force amplitudes at the vibration frequencies of nip N1. The oscillation frequency range of the nip is of the order o

^ 100 - 1000 Hz. The external force F is actively influenced by the vibration of the nip N1

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T 25 generating equipment for absorbing vibration energy from a vibration system.

00 ° Active external force F can be used as a generating device

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A hydraulic system 19, 19 'comprising a hydraulic actuator 10 such as a hydraulic cylinder 10 and a hydraulic pulse generator 21 comprising a rotating g spindle 29. The hydraulic pulse generator 21 can change the frequency and amplitude of the force F produced by the hydraulic cylinder 10.

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4 and 5 illustrate, according to some embodiments, caliper nipple vibration damping methods by means of feedback hydraulic systems 19 (Figure 5) and 19 '(Figure 6).

5 In the nipple vibration damping apparatus, force F is measured by force measurement 17, which may be based on measurement of pressure (e.g., between cylinder part 12) or force (e.g., between piston 11 and bearing housing 4) or strain structure (e.g., strain and load arm 7).

10 In the nipple vibration damping apparatus, the motion velocity x of the roll 2 support point is measured to measure the damping power P at the nip N1. The velocity x of the oscillation movement in the oscillation system is measured by an accelerometer 13 such as an industrial accelerometer. The acceleration sensor 13 may be mounted on the bearing housing 4 of the roller 2. The absolute accuracy 15 of the acceleration sensor 13 is not important for the application since maximum damping is sought for control regardless of the calibration of the acceleration sensor 13.

The phase angle Θ and the rotation frequency fi of the roll 2 are measured by a pulse encoder 14 connected to the roll 2 axis.

20

The measurement F of force F and the acceleration sensor measurement of the vibration movement rate x are multiplied by a factor 18 and integrated over a period of time to provide feedback y (t) on how the damping power supplied by the hydraulic actuator 10.21 has been affected.

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£! Control u (t) is a calender / nip load control that operates at low speed.

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For the damping control, one can make the multiple signals of the roll rotation frequency T from the measurement signals Q_ <0 until their variation is

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30 small enough. This method is known as STA (syncronized time σ> § averaging). The damping control has two parameters, the compensation force

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phase angle and amplitude. The adjustment can be accomplished using standard optimization algorithms, for example, Newtonian iteration or gradient search algorithms. Using Newton's 12 iterations, the instantaneous operating point is changed and the response change determines the magnitude of the next step.

In the damping control method, the phase angle 5 of the external compensation force F is adjusted so that a maximum damping power is sought or the damping power is maximized. In this case, the force F may also reduce the stiffness of the support, whereby a greater part of the kinetic energy is transmitted to the point to be damped. The amplitude of the damping force is increased until the damping power reaches its maximum.

10

When using one hydraulic pulse generator 21, only one frequency component can be adjusted at a time. This component can be selected, for example, according to the component of the largest oscillation spectrum. The rotating spindle 29 is adjusted, for example, by the servomotor M to rotate synchronously with the rotation of the roll, and the phase angle 15 is adjusted by optimization as described above.

When using an electric actuator such as piezo actuator 24 of FIG. 5, control of the feedback control loop for multiple frequency components at a time can be accomplished by damping control. In this case, a plurality of optimization loops 20 are performed in the control loop at a time. The loops can be independent of one another because different frequencies work independently of one another.

In Figures 4 and 5, the pressure response of the hydraulic cylinder 10 used in the roller support is increased by a hydraulic pulse generator 21. The first pressure line 20 'is led from the adjustable pressure source 20 to the hydraulic cylinder 10. A hydraulic pulse generator 21 is shown in Figures 6 and 7. The pressure side inlet 25 of the pulse generator 21 i is connected via a second pressure line 21 'to a first pressure line 20'. From the pulse generator 21, through the outlet 26, the tank line 23 'leads to the tank 23. The tank line 23' is provided with a choke 22 for changing the throttling of the flow of the tank line 23 '. With the pulse generator 21o, several hundred Flertz pressure responses can be achieved.

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The throughput of the pulse generator 21 can be arranged low and does not reduce the pressure p of the first pressure line 20 '.

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In Fig. 5, the feedback hydraulic system 19 'comprises (as opposed to the hydraulic system 19 of Fig. 4), in addition to the hydraulic pulse generator 21, a piezo actuator 24 for increasing the pressure response of the hydraulic cylinder 10 in addition to the hydraulic pulse generator 21. The piezo actuator 24 is capable of generating several hundred Hertz frequency oscillations. The frequency and amplitude of the force F produced by the hydraulic cylinder 10 can be varied by means of the piezo actuator 24.

The piezo actuator 24 may be integrated in the hydraulic cylinder 10. Integration of the piezo actuator 10 into the hydraulic cylinder 10 may reduce the damping of hydraulic pulses in the hydraulic fluid duct. In Figure 5, the hydraulic cylinder 10 comprises a cylinder member 12 at pressure p and a pressure chamber 12 'separated from the cylinder member 12 by a resilient pressure-sensitive wall 12'. The pressure chamber 12 'is arranged in pressure communication with the piezo actuator 24 by a third pressure pipe 24'. In the normal state, the piezo actuator 24 is arranged to be passive under compressive stress such that hydraulic fluid pressure p prevails in the pressure chamber 12 '. The use of the piezo actuator with the hydraulic cylinder 10 can provide simple mechanical coupling to provide active damping of roll vibrations.

20

The damping force range of a conventional hydraulic cylinder used in roller support extends up to about 50 Hertz without a pulse generator 21. The hydraulic system shown in Figures 4 and 5 with pulse generator 21 is for damping the vibration of the nipple N1 in the frequency range 100-1000 Hz.

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Figures 6 and 7 show a hydraulic pulse generator 21 which can be connected to a pressure line 21 operated by a pressure p on the hydraulic cylinder 10 used in the roller support. The pulse generator 21 preferably comprises a rotatable

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a valve stem 26 which, when rotated, opens and closes valve outlets 26. r5 30 The pulse generator 21 comprises an inlet 25 for hydraulic fluid o from the pressure line 21 'and preferably a plurality of outlets 26 to the tank line 23'.

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for hydraulic fluid. From the inlet 25, hydraulic fluid is led through a manifold chamber 27 to a valve chamber 28 having a rotatable spindle 29 for alternately opening and closing the outlets 26. The rotatable spindle 29 comprises a rotary shaft 29 'coupled to a motor M, for example a servomotor. Fig. 7 is a longitudinal sectional view of the pulse generator 21, and Fig. 6 is a cross-sectional view of the pulse generator 21 at a rotatable spindle 29 and 5 viewed from the direction of the inlet 25.

In Fig. 7, the pulse generator 21 comprises a first part 21a having an inlet 25 which engages the distribution chamber 27. The pulse generator 21 comprises a second part 21b pressurized to the first part 21a and provided with a rotatable spindle valve housing 28 which preferably passes through the second part 21b. The valve chamber 28 is in fluid communication with the outlets 26. The valve chamber 28 is open in the direction of the distribution chamber 27, from which the hydraulic fluid enters the valleys 29a between the ridges 29b on the outer periphery of the spindle 29. The rotary valve body is formed by the third part 21c of the pulse generator 21 15, against which the rotating spindle 29 rotates, and to which the second part 21b is pressurized. The third portion 21c comprises a plurality of outlets 26. Hydraulic fluid exits from the valve chamber 28 to the outlets 26, the valley points 29a of the spindle 29 being in rotation of the spindle 29 at the outlets 26.

20

The frequency of the pulse generator 21 is controlled by changing the rotational speed of the spindle 29 and the pressure amplitude is controlled by changing the throttle 22 of the outlets 26 or the tank line 23 '. If the tank line 23 'is completely closed, the pulse generator 21 will not affect the pressure control of the hydraulic cylinder 10.

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c \ j The damping solution can also be used in calendars other than those shown, such as soft calendars or multi-roll calendars. bottom roll

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Instead of x or in addition, the top roller can be loaded with hydraulic actuators.

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The solutions of some embodiments may also be used in other devices having rotating rollers or nip formed by rotating rolls.

C \ 1 Such devices include, for example, the press and roller of a paper machine and a winder.

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The foregoing description provides non-limiting examples of some embodiments of the invention. It will be apparent to one skilled in the art, however, that the invention is not limited to the details set forth, but that the invention may also be practiced in other equivalent ways.

Some features of the embodiments shown may be utilized without the use of other features. The foregoing description is to be construed as merely describing the principles of the invention and not limiting the invention. Thus, the scope of the invention is limited only by the appended claims.

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Claims (16)

An apparatus for controlling the driveability of a nip (N1), said nip (N1) formed between each other by a first roller (2) and a second processing means for a fiber web, which is a roller (3) or a belt, and the first the roller (2) is supported by the shafts at their ends by bearing sleeves (4) into a body (5), characterized in that the device comprises - a hydraulic actuator (10), such as a hydraulic cylinder adapted to produce external hydraulic damping force (F) to the support point (4) of the first roller (2) in the opposite direction to the speed of movement (x) of the vibration of the support point (4), and - a hydraulic pulse generator (21) whose pressure side (25) is in pressurized communication with the pressurized the cylinder part (12, p) in the hydraulic actuator (10) or with a pressure line (20, p) to adjust the frequency of the outer hydraulically produced damping force (F) to actuate at the phase of movement (x) opposite the phase. 2. Device for controlling the driveability of a nip (N1), which nip (N1) is formed between a first roller (2) and a second fiber web processing means, which is roller (3) or belt, and the first roller (2) is supported by the shafts at their ends by bearing sleeves (4) into a frame (5), characterized in that the device comprises - a hydraulic actuator (10), such as a hydraulic cylinder adapted to produce external hydraulic damping force ( F) to the supporting point (4) of the first roller (2) in the opposite direction to the speed of movement of the vibration of the supporting point (4), and - a piezo-driven hydraulic device (24) connected to the hydraulic section actuator (10) in pressurized connection to adjust the frequency and / or g amplitude of the outer hydraulically produced damping force (F) to affect CL Φ at the phase of movement (x) opposite phase. CO & 30 CD O O C \ l Device according to claim 1 or 2, characterized in that the device comprises a hydraulic pulse generator (21), whose pressure side (25) is in pressurized communication with the pressurized cylinder part (12, p) or pressure line (20 ') of the hydraulic actuator (10). p), to adjust the frequency of external hydraulically produced damping force (F) to act on the phase opposite to the speed of movement (x), and comprising a rotary valve spindle (29) and valve outlet (26) which are adjustable and opens to adjust the frequency of damping force (F) as the valve spindle (29) is rotated. Device according to any one of claims 1-3, characterized in that the device comprises throttle discharge (26) entering a hydraulic pulse generator (21) or a throttle (22) at a hydraulic fluid line (23 ') exiting said discharge (26). ) to adjust the amplitude of the damping force (F). Device according to any one of claims 1-4, characterized in that the device comprises a piezo-driven hydraulic device (24) which stays in pressurized (12 ', 12', 24 ') connection with a hydraulic adjusting device (10) to change the frequency. and / or the amplitude of the outer hydraulically produced damping force (F). 20 Device according to any one of claims 1-5, characterized in that the device comprises a measuring sensor (13, 14) suitable for measuring the speed (x) of the vibration, which is fixed to the point of support of the first roll (2), preferably the device comprises a tile. the bearing sleeve (4) attached acceleration sensor (13,14). § 25 cv Device according to any one of claims 1-6, characterized in that the device in § comprises a phase angle sensor (16) suitable for determining the rotation phase angle (Θ) of the first roller (2), preferably fixed at the end of the first roller (2). ω encoder. cd 30 05 Section 8. Device according to any of claims 1-7, characterized in that the device CM comprises a measurement (17) of the external damping force (F), which comprises a pressure sensor for measuring the pressure (p) in the cylinder (10) or a power sensor for measuring the force against the support point of the first roller (2) or an elongation meter to measure the elongation of the support structure (7). A method for checking the drivability of a nip (N1), which nip (N1) is formed between each other by a first roller (2) and a second processing means for a fiber web, which is a roller (3) or a belt, and the first the roller (2) is supported in the shafts at their ends by bearing sleeves (4) into a frame (5), characterized in that in the process: - produced at the supporting point (4) of the first roller (2) by a hydraulic actuator (10) such as a hydraulic cylinder external damping force (F), which acts in the opposite direction to the speed of movement of the vibration point of the support point (4), - the frequency of external hydraulically produced damping force (F) is adjusted to affect the phase of movement (x) opposite the phase through the hydraulic the pressurized cylinder part (12, p) of the actuator (10) or a combined hydraulic pulse generator (21) of a pressure line (20 ', p) Method according to claim 9, characterized in that in the method: - the speed of movement (x) of the nip vibration is measured from the support point (4) of the first roll (2) 20. the rotational phase angle of the first roll (2) is measured - external damping force (F) is produced. in the opposite direction to the speed of movement (x) to the support point (4) of the first roller (2), through a hydraulic actuator (10) such as a hydraulic cylinder, 0. the external hydraulically produced damping force (F) is measured, 25. the frequency is adjusted by the external hydraulic produced the damping force (F) to act at the opposite phase to the speed of movement (x) through a hydraulic pulse generator (21) coupled to the pressure line (20 ') of the hydraulic actuator (10). CC CL 11. A method according to claim 9 or 10, characterized in that in the method CD 30 external damping force is actively produced by measuring the motion amplitude of the first CD o the support point (4) of the roller (2) and adjusting the amplitude and C \ l phase angle of the damping force. in relation to the phase angle of the roller to maximize the damping effect (P) · Method according to any one of claims 9-11, characterized in that the method adjusts the frequency of external hydraulically produced damping force (F) by changing the rotational speed of a valve spindle (29) of a hydraulic pulse generator (21) comprising a hydraulic pulse generator. rotatable valve stem (29) which opens and closes valve outlet (26) as it is rotated. Method according to any one of claims 9-12, characterized in that in the method the amplitude of external hydraulically produced damping force 10 (F) is adjusted by changing the throttle of the hydraulic pulse generator (21) discharge (26) or the throttle of the tank line (23 '). from said discharge (26) to a tank (23). Method according to any of claims 9-13, characterized in that in the method for measuring external hydraulically produced damping force (F), the pressure (p) in the hydraulic cylinder (10) or the force (F) measured the first roller (2) of the hydraulic cylinder (10) acts against the point of support or the elongation of the support structure of the first roller (2) is measured. Method according to any one of claims 9-14, characterized in that in the method the measurements for adjusting the damping force (F) are performed by forming multiple components of the rotational frequency (fi) of the roller by taking averages of the measurements for movement speed, phase angle and force (x , 0, F) until the variation of the multiple components is small enough. o o 25 Method according to any of claims 9-15, characterized in that in the cvj process the damping effect (P) is maximized by the optimization algorithm in oo using as the parameter the phase angle and amplitude of the damping force, x which damping effect (P) is the product of the damping force (F ) and vibration CL (x). CD fc 30 CD O O C \ l