JP2003097541A - Method of suppressing deformation of nip roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the angular deformation of nip rolls contacting each other and reduce the vibration accompanying the deformation. SOLUTION: The ratio of the diameter of a first nip roll 1 to that of a second nip roll 2 is set to be a value different from 1 to avoid the number of angular shapes of the rolls 1, 2 from being integer values or nearly integer values.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for suppressing the deformation of nip rolls used in a size press process of a papermaking machine.

[0002]

2. Description of the Related Art For example, in a size press process of a papermaking machine, paper is pressed by two nip rolls that are in pressure contact with each other.

[0003]

The papermaking machine industry tends to be faster. However, each of the nip rolls described above tends to vibrate particularly when rotating at a high speed, which is a bottleneck in increasing the speed. This vibration causes the same portion of each roll to strongly nip due to the relationship between the rotation speed of each roll and the natural frequency of the vibration system including each roll and its supporting means, and these rolls are deformed into a polygonal shape. It is due to doing. Conventionally, since the diameter ratio of each nip roll is set to 1, those same portions strongly nip, which causes a large vibration due to the polygonal shape.

As a means for coping with the deformation of the nip rolls, it is conceivable to increase the diameter of these rolls. This is because if the diameter of the roll is increased, the number of rotations of the roll is reduced and the recovery time for the deformation is secured, that is, the growth of deformation is eliminated. However, such a countermeasure causes an increase in roll cost and an increase in installation space.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to suppress angular deformation of nip rolls in contact with each other and to reduce vibration generated due to the deformation.

[0006]

SUMMARY OF THE INVENTION The present invention is a method for suppressing deformation of first and second nip rolls that nip a sheet material, wherein the diameter ratio of the first and second nip rolls is 1. I am trying to set different values. According to the present invention, strong nipping of the same portion of the first and second nip rolls is avoided in a predetermined operating speed range, and polygonal deformation of each roll is suppressed.

The diameter ratio of the first and second nip rolls is defined by the ratio of the vibration frequency of the vibration system including these rolls to the rotation speed of the first nip roll, and the polygonal polygonal polygonal number of the rolls. Is an integer value N ₁ , the polygon number of the polygonal deformation of the roll defined by the ratio of the vibration frequency of the vibration system to the rotation speed of the second nip roll is set to have the following value. be able to. N ₁ ± j + a Here, j = 0,1,2,3, ... 0 <a <1 By setting the polygon number of the second nip roll in this way,
Since it is avoided that both the number of polygons of the first nip roll and the number of polygons of the second nip roll become integer values, polygonal deformation of those rolls is suppressed.

The value a may be set to 0.1 to 0.9, and more preferably set to 0.5. Further, the first and second nip rolls are effective as, for example, nip rolls provided in a size press process of a papermaking machine.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a pair of nip rolls 1 and 2 provided in a size press process of a papermaking machine, for example. Further, FIG. 2 shows a model of a vibrating system including the rolls and their supporting means. In FIG. 1, the top roll 1 and the bottom roll 2 each have a surface layer formed of rubber having a thickness of 20 mm,
The paper 3 sent from the previous step (drying step) is nipped. The bottom roll 2 is biased toward the top roll 1 by the abutting force of the pressing member 4 which is swingably supported.

The rolls 1 and 2 are polygonal in relation to the number of rotations thereof and the natural frequency of the vibration system (see FIG. 2) including their supporting means and the like. This polygonalization means a phenomenon in which the same part of each roll 1, 2 is repeatedly deformed by being strongly nipped, and the deformation gradually grows to form a polygonal pattern. This phenomenon occurs when the values of the natural frequency / roll speed of each of the rolls 1 and 2 are both integers or near integers.
Here, one of the top roll 1 and the bottom roll 2 is a reference roll and the other is a counterpart roll, and the ratio of the diameter D _{1 of the} reference roll to the D ₂ of the counterpart roll is γ = D ₂ / D ₁ ... ( 1), the polygon number of the polygonal deformation pattern of these rolls is expressed as follows. Number of squares of reference roll n ₁ = 60πD ₁ f ₀ / V (2) Number of squares of counterpart roll n ₂ = 60πD ₂ f ₀ / V = 60πγD ₁ f ₀ / V (3) Where, f ₀ : Natural frequency (Hz) of the vibration system shown in FIG. 2 V: Standard paper feed speed (m / min)

FIG. 3 shows that when the natural frequency f ₀ is 89 Hz and the diameter ratio of each roll is 1.0, the rotation speed of the reference roll is changed in the range of 3 to 8 Hz (of course, rotation of the mating roll). The number of squares of each roll when the number of the rolls is changed to the same peripheral speed), and FIG. 4 shows the same relation when the diameter ratio of each roll is 1.27. There is.

When the diameter ratio of the rolls is 1.0 (the same diameter), the polygons of the rolls are always the same, so that the numbers of polygons n ₁ and n _{2 of} these rolls are both integers. Frequently occurs in the above rotation speed range. On the other hand, when the diameter ratio of each roll is 1.27, the number of polygons of each roll becomes an integer or near an integer only at the points indicated by circles. The fact that the number of polygons of each roll is not an integer means that the same portions of each roll do not nip strongly, that is, the growth of the polygonal deformation pattern is suppressed.

In order to theoretically show this, when the unstable region due to polygonal deformation is calculated using the diameter ratio as a parameter, it becomes as shown in FIGS. The calculation result is for the case where the diameter of the reference roll is 1525 mm. In each figure, the horizontal axis represents the paper feed speed (machine speed), and the vertical axis represents the bottom damping amount (corresponding to the vibration acting force on the support system). The bell-shaped attenuation amount line in each figure shows a peak at the paper feed speed at which the number of squares of each roll becomes an integer or near an integer. The region surrounded by the bell-shaped line is an unstable region due to polygonal deformation.

As is clear from the comparison between FIG. 5 and FIGS. 6 to 11, the diameter of the mating roll is the diameter of the reference roll 152.
When it is made different from 5 mm, the unstable region is reduced.
In each figure, the lower the paper feeding speed is, the smaller the unstable region is, and the lower the paper feeding speed is, the longer the recovery time from the deformed state is secured.

As is clear from the above consideration, the pattern of angular deformation is likely to occur when both the square numbers n ₁ and n ₂ of the reference roll and the mating roll are integers or near integers. Therefore, the standard paper feed speed V
When the square number of the reference roll is an integer at or near the (standard peripheral speed of the reference roll and the partner roll), or if the square number of the mating roll is prevented from becoming an integer or near the integer, a certain paper feed speed range Therefore, the generation of the angular deformation pattern is suppressed.

Therefore, a method for preventing the polygon number of the mating roll from becoming an integer when the polygon number of the reference roll becomes an integer will be described below. In the above formula (1), an integer number of polygons N ₁ determined when the same speed is changed in the vicinity of the standard paper feed speed V is defined, and the same speed at that time is defined as V ₀ . The number of squares of the reference roll is an integer value N ₁
, The condition for not making the square number n ₂ of the opponent roll an integer is given by the following equation. n ₂ = N ₁ ± j + a (4) Here, j = 0, 1, 2, 3, ... 0 <a <1 From the above equations (3) and (4), the above diameter ratio γ To decide. At this time, V ₀ is used as the speed V in the equation (3).

The diameter ratio γ (≠
1) The diameter D ₁ of the reference roll and the counterpart roll so that
If D ₂ is set, the number of polygons of these rolls is prevented from becoming an integer, so that the generation of the angular deformation pattern is suppressed in the vicinity of the standard paper feed speed. In addition,
The coefficient a in the above equation (4) may be set to a value in the range of 0.1 to 0.9, preferably 0.4 to 0.6, more preferably 0.5.

Next, a concrete example will be described.
Assuming that the diameter D _{1 of the} reference roll is 1.5 m, the natural frequency of the vibration system is 89 Hz, and the standard paper feed speed V is 1700 m / min, the number n of squares of the reference roll can be calculated from the formula (2).
₁ is calculated as n ₁ = 60π × 1.5 × 89/1700 = 14.8. The integer angular coefficient N ₁ closest to the polygon number n ₁ = 14.8 is N ₁ = 15. Therefore, the paper feed speed V _{0 in which} a pattern of angular deformation is likely to occur in the vicinity of the standard paper feed speed V is n ₁ = N ₁ = 1 in the above equation (2).
It's 5 This velocity V ₀ is calculated based on the equation (2) as follows: V ₀ = 60π × 1.5 × 89/15 = 1678 m / mi
Calculated as n.

The angular coefficient n _{1 of the} reference roll is n ₁ = N ₁ = 15
In order to prevent the occurrence of angular deformation patterns,
Based on the formula (4), the number of squares n ₂ of the partner roll is set to n ₂
= 15 ± j + a. The number of polygons n ₂ is
When set to n ₂ = 15 + j + a, and when n ₂ = 15-j
Comparing the case where + a is set, the above equation (1),
From the relationship of (3), the diameter of the opponent roll is set to be larger in the former case than in the latter case.

From the viewpoint of more effectively preventing the generation of the angular deformation pattern, it is advantageous to increase the diameter of the mating roll. This is because at a predetermined paper feed speed, the larger the diameter of the roll, the longer the recovery time from the deformation of the roll is secured.
On the other hand, from the viewpoint of cost reduction, it is not desirable to make the diameter of the mating roll too large.

Therefore, in this embodiment, n ₂ = 15 + j
+ A and j = 0. In this case, if an optimum value of 0.5 is given as a, then n ₂ = 15 + 0.5 = 15.5. Then, the calculated value V is calculated as the speed V in the equation (3).
Given ₀ = 1678, the diameter ratio γ is calculated as γ = 15.5 x 1678 / 60π x 1.5 x 89 = 1.034. Therefore, the optimum diameter of the mating roll for preventing the occurrence of the angular deformation pattern is expressed by the above formula (1).
Therefore, D ₂ = 1.304 × 1.5 = 1.55 m.

In FIG. 12, line a shows the relationship of the number of squares of each roll when the reference roll and the counterpart roll have the same diameter (1.5 m), and line b shows the reference roll diameter of 1. 5m, opponent roll diameter D ₂ is 1.55m
The same relationship in the case of the above-mentioned embodiment set to, and the line c shows the relationship between the number of squares of the reference roll and the paper feeding speed, respectively.

As is apparent from FIG. 12, when the reference roll and the mating roll have the same diameter (1.5 m), 150
In the paper feed speed range of 0 to 2000 m / min, a state where the number of squares of those rolls is an integer frequently occurs (see the circle on line a). this is,
When the paper feed speed is changed from the standard paper feed speed V,
This means that there is a greater chance that the angular deformation pattern will occur on each roll.

On the other hand, according to the above embodiment in which the diameter ratio of each roll is set so as to satisfy the relationship of the line b,
In the paper feed speed range of 1500 to 2000 m / min, the state where the numbers of polygons of the rolls are both integers does not occur. Therefore, in the high-speed paper feed speed range, it is possible to suppress the generation of the angular deformation pattern on each roll, and execute an appropriate size press without vibration. Incidentally, in the relationship shown by the line b in FIG. 12, as indicated by the dotted line, when the polygon number n ₁ of the reference roll is about 13.2, the polygon number n ₂ of the partner roll is about 13.
Become 7. At this time, the paper feed speed is about 1900 m.
/ Min.

In the above embodiment, the present invention is applied to the nip roll used in the size press process of the papermaking machine, but the present invention is applied to the nip roll used in the press process, calender process, etc. of the machine, or It can also be effectively applied to nip rolls used in printing machines. The present invention is also effective for suppressing deformation of resin or metal nip rolls.

[0026]

According to the present invention, the diameter ratio of the first and second nip rolls is set to a value different from 1, so that the first and second nip rolls are operated in a predetermined operating speed range. It is avoided that the same portion of the roll is strongly nipped, and polygonal deformation of each roll is suppressed. Therefore, it is possible to prevent the vibration trouble due to the polygonalization of the nip rolls and reliably nip the sheet material such as paper to make the sheet travel stably, which contributes to the high-speed traveling of the sheet material. Moreover, since the stable running can be realized without reducing the diameter of the roll or increasing the diameter of the roll too much, the application system of the papermaking machine or the like can be operated at a high speed without increasing the size or the cost. Can be converted.

[Brief description of drawings]

FIG. 1 is a conceptual diagram illustrating an arrangement mode of nip rolls provided in a size press process of a paper manufacturing machine.

FIG. 2 is an equivalent model diagram of a vibrating system including the nip rolls of FIG.

FIG. 3 is a graph exemplifying the relationship between the number of squares of each roll when the diameter ratio between the reference roll and the counterpart roll is set to 1.

FIG. 4 is a graph exemplifying the relationship of the number of squares of each roll when the diameter ratio of the reference roll and the counterpart roll is set to 1.27.

FIG. 5 is a graph exemplifying the relationship between the paper feed speed and the bottom attenuation amount when the diameter ratio between the reference roll and the counterpart roll is set to 1.

FIG. 6 is a graph exemplifying a relationship between a paper feed speed and a bottom attenuation amount when a diameter ratio between a reference roll and a counterpart roll is set to 0.95.

FIG. 7 is a graph exemplifying the relationship between the paper feed speed and the bottom attenuation amount when the diameter ratio between the reference roll and the counterpart roll is set to 0.90.

FIG. 8 is a graph exemplifying a relationship between a paper feed speed and a bottom attenuation amount when a diameter ratio between a reference roll and a counterpart roll is set to 0.85.

FIG. 9 is a graph illustrating the relationship between the paper feed speed and the bottom attenuation amount when the diameter ratio between the reference roll and the counterpart roll is set to 1.09.

FIG. 10 shows a diameter ratio of the reference roll to the counterpart roll of 1.17.
6 is a graph illustrating the relationship between the paper feed speed and the bottom attenuation amount when set to.

FIG. 11 shows a diameter ratio of the reference roll to the counterpart roll of 1.27.
6 is a graph illustrating the relationship between the paper feed speed and the bottom attenuation amount when set to.

FIG. 12 is a graph illustrating a relationship between the number of squares of a reference roll and a counterpart roll and a relationship between a reference roll and a paper feed speed in a specific example of the present invention.

[Explanation of symbols]

1 top roll 2 bottom roll 3 paper

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoji Miura             Hiroshima Prefecture Mihara City Itozakicho 5007 Mitsubishi Heavy Industries             Paper and printing machinery division (72) Inventor Juno Sueoka             1-9-4 Kashiihama, Higashi-ku, Fukuoka City, Fukuoka Prefecture (72) Inventor Takahiro Liu             5-1 Uedacho, Oita City, Oita Prefecture F term (reference) 3J103 AA02 AA12 AA85 BA34 BA37                       BA43 FA04 GA02 GA33 GA54                       GA55 HA03 HA31 HA41                 4L055 CE72 CE90 FA22

Claims (5)

[Claims] 1. A method for suppressing deformation of first and second nip rolls that nip a sheet material, wherein a diameter ratio of the first and second nip rolls is set to a value different from 1. And a method for suppressing the deformation of the nip roll. 2. The diameter ratio of the first and second nip rolls is defined by the ratio of the frequency of the vibration system including these rolls to the rotation speed of the first nip roll, and the polygonal deformation of the rolls. When the number of polygons is an integer value N ₁ , the number of polygons of polygonal deformation of the roll defined by the ratio of the frequency of the vibration system to the rotation number of the second nip roll has the following value. The method for suppressing deformation of a nip roll according to claim 1, wherein the deformation is set. N ₁ ± j + a where j = 0, 1, 2, 3, ... 0 <a <1 3. The nip roll deformation suppressing method according to claim 2, wherein the a is set to 0.1 to 0.9. 4. The nip roll deformation suppressing method according to claim 2, wherein the a is set to 0.5. 5. The nip roll deformation suppressing method according to claim 1, wherein the first and second nip rolls are nip rolls provided in a papermaking machine or a printing machine.