JP7484435B2 - Method for predicting occurrence of roller polygonization phenomenon and method for changing natural frequency of conveying system - Google Patents

Description

The present invention relates to a web conveying device, a method for identifying the vibration mode of a roller, and a method for changing the natural frequency of a conveying system.

Among the devices that transport webs such as paper or plastic films, there are many that use two rollers to pinch the web while transporting it for the purpose of tension cutting to separate the tension on the upstream and downstream sides, controlling the thickness of the web, and blocking accompanying flows when applying surface treatment to the web. Examples of such devices include the press rollers of papermaking machines in the papermaking industry, rolling rollers in the steel industry, and nip rollers in corona treatment devices in the film production industry.

In a web transport device that uses two rollers as described above to clamp and transport a web, it is known that under certain conditions, when the rotational frequency of the rollers and the natural frequency of the transport system that makes up the device match or approach each other, resonance occurs, causing the rollers that make up the device to vibrate. If the vibration increases due to resonance, it can lead to poor processing of the web or machine failure.

To address this issue, Patent Document 1 proposes a technology that continuously measures the roller's vibration speed, compares it with a predetermined reference value to determine whether resonance is occurring, and, after resonance is detected, changes the temperature of the coating on the roller to control the natural frequency of the conveying device and suppress vibration.

Japanese Patent Application Laid-Open No. 9-176982

However, a special resonance phenomenon occurs in conveying devices with long rollers, which causes the surface of the rollers to periodically deform and wear, a phenomenon known as polygonization, and it was found that this problem could not be solved by applying the technology in Patent Document 1.

It is known that when a long roller rotates, its own imbalance generates vibration components called harmonics that are integer multiples of the rotational frequency, and the phenomenon in which harmonics resonate with the natural frequency of the conveying system is called harmonic resonance.

When harmonic resonance occurs, as described above, multiple vibrations occur during one rotation of the roller, and the roller hits the opposing roller, causing the polygonal phenomenon. Once polygonal phenomenon occurs, the roller's surface unevenness becomes more pronounced, and vibrations continue to increase. Therefore, in order to prevent polygonal phenomenon, it is important to detect harmonic resonance early and avoid it. Furthermore, in order to detect the occurrence of harmonic resonance, it is necessary to identify the vibration state of the roller, known as the vibration mode.

However, the technology in Patent Document 1 simply measures the roller vibration speed and cannot identify the vibration mode that leads to the polygonal phenomenon.

Therefore, the present invention provides a method for identifying the vibration mode of a web conveying device and rollers that can solve the above problems, detect harmonic resonance early, and prevent the occurrence of polygonalization.

[1] The web conveying device of the present invention which solves the above problems,
Two rollers that convey the web while clamping it;
a vibration measuring device for measuring the longitudinal center position of each of the surfaces of the two rollers;
and a calculator that identifies the vibration mode of the two rollers from the vibration data measured by the vibration measuring device.

[2] A web transport device according to another aspect of the present invention that solves the above-mentioned problems is a web transport device that transports a web,
Two rollers that convey the web while clamping it;
a vibration measuring device for measuring the surface of each of the two rollers at positions 1/4, 1/2, and 3/4 of the longitudinal length from one end of the roller;
and a calculator that identifies the vibration mode of the two rollers from the vibration data measured by the vibration measuring device.

[3] A web transport device according to another aspect of the present invention that solves the above problems is a web transport device that transports a web, comprising: two rollers that transport the web while pinching it; and a roller that contacts one of the two rollers without pinching the web during web transport;
a vibration measuring device for measuring vibrations at a longitudinal center position on the surface of each of the two rollers that contact the web without pinching it;
and a calculator that identifies a vibration mode of two rollers that are in contact with the web without pinching the web, based on vibration data measured by the vibration measuring device.

[4] A web transport device according to another aspect of the present invention that solves the above problems is a web transport device that transports a web,
two rollers for conveying the web while pinching it, and a roller for contacting one of the two rollers without pinching the web while the web is being conveyed;
a vibration measuring device for measuring vibrations at positions 1/4, 1/2, and 3/4 of the longitudinal length from one end of the rollers on the surface of each of the two rollers that contact the web without clamping it;
and a calculator that identifies a vibration mode of two rollers that are in contact with the web without pinching the web, based on vibration data measured by the vibration measuring device.

[5] The web transport device of the present invention has a transport system that is a structural unit composed of at least two rollers that transport the web while clamping it, and a support that rotatably supports these two rollers, and preferably has a natural vibration variable means that can change the natural frequency of the entire transport system.

[6] The method of identifying the vibration mode of the rollers of the present invention, which solves the above problem, identifies the vibration mode of the two rollers from the vibration data obtained by measuring the vibration at the center position in the longitudinal direction of the surface of each of the two rollers that convey the web while clamping it.

[7] Another method for identifying the vibration mode of the rollers of the present invention that solves the above problem is to identify the vibration mode of the two rollers from the vibration data measured on the surface of each of the two rollers that convey the web while clamping it, at positions 1/4, 1/2, and 3/4 of the longitudinal length from one end of the roller.

[8] Another method for identifying the vibration mode of the rollers of the present invention that solves the above problem is to identify the vibration mode of the two rollers that are in contact with the web without clamping it, from vibration data measured at the longitudinal center of the surface of one of the two rollers that transport the web while clamping it, and of the surface of the roller that is in contact with the one roller without clamping the web.

[9] Another method for identifying the vibration mode of the rollers of the present invention that solves the above problem is to identify the vibration mode of the two rollers that are in contact with the web without clamping it from vibration data measured on the surface of one of the two rollers that convey the web while clamping it, and on the surface of the roller that is in contact with the one roller without clamping the web, at positions 1/4, 1/2, and 3/4 of the longitudinal length from one end of the roller.

[10] The method of changing the natural vibration frequency of a conveying system of the present invention, which solves the above problem, uses a structural unit of at least two rollers that convey the web while clamping it, and a support that rotatably supports these two rollers as a conveying system, and when it is determined that a roller is vibrating using the roller vibration mode identification method of the present invention, changes the natural vibration frequency of the entire conveying system.

[11] In the method for changing the natural frequency of a conveyor system of the present invention, the natural frequency of the conveyor system is preferably changed by ω/2 [Hz].
however,
ω=V/(D·π)
ω: Rotation frequency of one of the rollers from which vibration data was obtained [Hz]
V: web transport speed [m/sec]
D: Diameter [m] of any one of the rollers from which vibration data was obtained.

[Terminology explanation]
Next, the meaning of each term in the present invention will be explained.
"Web" refers to a long thin member such as paper, cloth, plastic film, metal foil, thin steel plate, etc. There is no restriction on the material.
The term "conveying device" refers to a device that sends a web from upstream to downstream in the longitudinal direction. In this specification, at least two rollers that hold the web and a group of rollers in contact with them are considered to be one conveying device.
In this specification, the term "vibration measuring device" refers particularly to a device that measures the displacement of the roller surface in the radial direction of the roller. Generally, this refers to a laser displacement meter or the like.
The term "vibration mode" refers to a state or form of vibration, and in this specification, it particularly refers to the vibration state of a roller or a conveying system that occurs at a specific frequency.
The term "computer" refers to a device that analyzes vibration displacement data and identifies the occurrence of resonance and the vibration mode.
The term "conveyor system" refers to a structural unit that is constituted at least by two rollers that hold the web and a support that rotatably supports these two rollers.
"Natural frequency" refers to the resonant frequency inherent to a substance or system. A substance or system has multiple natural frequencies, and resonance occurs at each natural frequency. The state or form of vibration is called a vibration mode.

According to the present invention, by measuring the vibration of each of the two rollers that clamp the web, or the vibration of each of the two rollers that contact the web without clamping it, and calculating the measured vibration data to identify the vibration mode, it is possible to detect the occurrence of harmonic resonance that leads to the polygonal phenomenon at an early stage.

1 is a schematic side view showing an embodiment of a web transport device of the present invention. 1 is a schematic side view showing a state in which the nip is open in one embodiment of a web transport device of the present invention. 1 is a conceptual diagram of harmonics generated in a typical web transport device. FIG. 1 is a conceptual diagram showing resonance occurring in a primary vibration mode of a single nip roller in a typical web transport device. FIG. 1 is a conceptual diagram showing a case in which resonance occurs in the primary vibration mode of a single receiving roller in a typical web transport device. FIG. 1 is a conceptual diagram showing a case in which resonance occurs in a first vibration mode of the same phase of a nip system in a typical web transport device. FIG. 1 is a conceptual diagram showing a case in which resonance occurs in a nip system antiphase first vibration mode in a typical web transport device. FIG. 1 is a conceptual diagram showing resonance occurring in a secondary vibration mode of a single nip roller in a typical web transport device. FIG. 1 is a conceptual diagram showing resonance occurring in a third vibration mode of a single nip roller in a typical web transport device. 1 is a conceptual diagram showing the relationship between a vibration source generated in a typical web transport device and the natural frequency of the web transport device. 4 is a flowchart showing one embodiment of a method for identifying a vibration mode of a roller of the present invention. 1 is a conceptual diagram showing the results of measuring the vibration of a typical web transport device. FIG. 13 is a conceptual diagram obtained by frequency analysis of vibration data of a nip roller of the web transport device shown in FIG. 12 . FIG. 13 is a conceptual diagram obtained by frequency analysis of vibration data of a receiving roller of the web transport device shown in FIG. 12 . FIG. 15 is a conceptual diagram showing the frequency analysis results of FIG. 13 and FIG. 14 together. FIG. 16 is a conceptual diagram showing identical or adjacent frequency components extracted from the frequency components shown in FIG. 15 . FIG. 17 is an example of a conceptual diagram in which an inverse Fourier transform is performed on the frequency components extracted in FIG. 16 . 17 is another example of a conceptual diagram in which an inverse Fourier transform is performed on the frequency components extracted in FIG. 16 . 1 is a schematic side view of one embodiment of a prior art web transport device; 1 is a conceptual diagram showing the relationship between speed and frequency of rotational frequency and harmonics generated in a web transport device of the prior art. 1 is another form of conceptual diagram showing the rotational frequency and harmonics generated in a prior art web transport device as a function of speed and frequency. 1 is another form of conceptual diagram of harmonics generated in a typical web transport device. 1 is a schematic side view showing one embodiment of a web transport device of the present invention. 1 is a schematic overhead view showing one embodiment of a web transport device of the present invention. FIG. 1 is a conceptual diagram showing a case in which resonance occurs in a nip system antiphase secondary vibration mode in a typical web transport device. 1 is a schematic overhead view showing another embodiment of a web transport device of the present invention. FIG. 2 is a conceptual diagram showing the relationship between speed and frequency of the rotational frequency and harmonics generated in the web transport device of the present invention. FIG. 2 is another form of conceptual diagram showing the rotational frequency and harmonics generated in the web transport device of the present invention in terms of the relationship between speed and frequency. 4 is a schematic side view showing another embodiment of the web transport device of the present invention. FIG. 4 is a schematic side view showing another embodiment of the web transport device of the present invention. FIG. 4 is a schematic side view showing another embodiment of the web transport device of the present invention. FIG. FIG. 1 is a conceptual diagram showing the relationship between speed and frequency of rotational frequency and harmonics generated in a typical web transport device. 1 is a schematic side view showing a web conveying device according to a first embodiment of the present invention; FIG. 1 is a conceptual diagram showing the relationship between speed and frequency of rotational frequency and harmonics generated in a web transport device of Comparative Example 1. FIG. 2 is a conceptual diagram showing the relationship between speed and frequency of the rotational frequency and harmonics generated in the web transport device of the first embodiment. FIG. 10 is a conceptual diagram showing the relationship between the speed and the frequency of the rotational frequency and harmonics generated in the web transport device of Comparative Example 2. FIG. 10 is a conceptual diagram showing the relationship between the speed and the frequency of the rotational frequency and harmonics generated in the web conveying device of the second embodiment.

The web conveying device, the method for identifying the vibration mode of a roller, and the method for changing the natural frequency of a conveying system of the present invention will be described below with reference to the drawings. Note that the present invention is not to be interpreted as being limited thereto.

A schematic side view of one embodiment of the web transport device of the present invention is shown in Fig. 1. Note that Fig. 1 shows only the main parts, and the frame for fixing the rollers, cylinder 4, etc. is omitted.
The web transport device in Fig. 1 is composed of a nip roller 1 and a receiving roller 2. The receiving roller 2 has a bearing 7 rotatably fixed to a frame, and the nip roller 1 is supported by an arm 5 whose shaft is rotatable. A vibration measuring device 13 is installed at the center of the longitudinal direction of both rollers, and a calculator 20 is installed to calculate the measurement data and identify the vibration mode. In addition, the nip can be opened and closed by switching a cylinder 4 attached to the arm 5 of the nip roller 1 as shown in Fig. 2.

The material of the core metal of the nip roller 1 and the receiving roller 2 is not particularly limited, but metal materials such as carbon steel, stainless steel, and aluminum alloys, and carbon fiber composite materials using carbon fiber as a reinforcing material and resin as a base material can be used as appropriate.

The materials used to cover the nip roller 1 and the receiving roller 2 are not particularly limited, but they may be covered with rubber 3 to suppress the effects of uneven thickness of the web 6 and the manufacturing accuracy of the roller surface. The type of rubber 3 is not particularly limited, but for example, natural rubber, nitrile rubber, chloroprene rubber, ethylene propylene rubber, silicone rubber, chlorosulfonated polyethylene rubber, urethane rubber, fluororubber, and mixtures thereof can be used as appropriate depending on the purpose and environment of use. Furthermore, in order to reduce the effects of differences in deflection between rollers, the outer diameter of the rubber 3 may be gradually reduced from the center to the ends, giving it a so-called crown shape. It may also be a single layer or multiple layers such as two or three layers.

The structure of the nip roller 1 and the receiving roller 2 is not particularly limited, but a single-shaft structure having a solid cylindrical or hollow cylindrical core metal, or a double-tube structure having a cylindrical core metal on the outside and a solid cylindrical or hollow cylindrical core metal on the inside can be used as appropriate. The core metal may be made of a single piece, or it may be a so-called joint structure in which multiple core metals are connected. A structure having a flow path inside for circulating a heat medium and capable of controlling the surface temperature can also be used.

The operating mechanism of the nip roller 1 is not particularly limited, but for example, an air cylinder that uses air as the working fluid, an oil cylinder that uses oil, an air-hydro cylinder that uses air and oil on the primary and secondary sides, respectively, a linear motor system that uses electromagnets, etc. can be used as appropriate. Of these, an air-hydro cylinder that utilizes the simplicity of air pressure and the damping capacity of hydraulic pressure can be preferably used.

The type of web 6 to be transported is not particularly limited, but examples include paper, cloth, plastic film, metal foil, and thin steel plate. In particular, plastic films that can be used include polyethylene terephthalate, polyethylene naphthalate, polypropylene, polystyrene, polycarbonate, polyimide, polyphenylene sulfide, nylon, aramid, and polyethylene. They can also be used as copolymers or polymer alloys. Polymer alloys here refer to multi-component polymer systems, such as block copolymers formed by copolymerization, and polymer blends formed by mixing, etc.

There are no particular limitations on the method of measuring vibration, but for methods of directly measuring displacement, contact types such as transformer type and scale type vibration measuring instruments can be used as appropriate, while non-contact types such as optical type, eddy current type, ultrasonic type, and laser focus type vibration measuring instruments can be used as appropriate. In addition, a method of calculating displacement from acceleration measured using a piezoelectric acceleration sensor can also be used as appropriate. Of these, laser focus type displacement meters are preferably used because they are non-contact types that do not cause scratches on the roller or web, have a long focal length, and are highly accurate.

Here, we will explain the harmonics that are generated when a roller rotates. When a long roller rotates, it is known that vibrations of an integer multiple frequency are generated during one rotation of the roller due to imbalance components resulting from the machining and assembly accuracy of the core metal, coating, shaft, etc. that make up the roller, and vibrations transmitted from parts that support the roller such as bearings, arms, and cylinders, and from devices that drive the roller such as motors, belts, and couplings. These integer multiple vibration components are called harmonics. Figure 3 shows a conceptual diagram of harmonics generated in a typical web transport device. As shown in Figure 3, the vibration components have the strongest intensity at the rotation frequency, and the higher the order of the harmonics, the weaker their intensity becomes.

Here, we will explain the polygonal phenomenon. It is known that polygonal phenomenon occurs when harmonic resonance occurs in the conveying system, and deformation and wear occur on the surface of a rotating body such as a rubber roller, a metal roller, or a ball of thread in a sinusoidal constant cycle. In the paper industry, press rollers in the papermaking process, in the steel industry, hot leveler rollers that correct the shape defects of plates in the rolling process, in the silk industry, wound up balls of thread in the winding process, and in the film film industry, nip rollers in the corona treatment process are known. In this invention, the number of surface undulations that occur in the polygonal phenomenon is called the number of sides for convenience. In addition, the number of sides of the polygonal phenomenon differs depending on the conveying system. For example, it has been reported that press rollers in the papermaking process in the paper industry have 6 to 9 sides, hot leveler rollers in the rolling process in the steel industry have 35 to 60 sides, balls of thread in the silk industry have 2 to 3 sides, and nip rollers in the film film industry have 6 to 13 sides. The number of sides of these polygonal phenomena corresponds to the order of the harmonic of the rotating body that is the source of vibration.

Here, we will explain the vibration modes and orders that occur in a typical web transport device consisting of two rollers. In a web transport device consisting of a nip roller and a receiving roller, four vibration modes are roughly generated.
The first vibration mode is one in which vibration occurs in the nip roller alone, as shown in FIG.
The second vibration mode is one in which vibration occurs in the receiving roller alone, as shown in FIG.
The third is a nip-based in-phase vibration mode in which both rollers vibrate simultaneously and in the same direction, as shown in FIG.
The fourth is a nip-type antiphase vibration mode in which both rollers vibrate simultaneously and in opposite directions, as shown in FIG.

Furthermore, each vibration mode has an order. The order of a vibration mode refers to a state in which the vibration with both ends as nodes is the primary order when both ends are fixed, and increases by one for each additional node. Note that the orders in Figures 4 to 7 correspond to the primary order. For reference, Figures 8 and 9 show conceptual diagrams of when secondary and tertiary vibration modes occur in a single nip roller 1.

Here, we will explain resonance that can occur in a typical web transport device. Generally, resonance refers to a phenomenon in which vibration increases when the vibration source, which is the source of vibration, and the natural frequency of an object match or approach each other. In the case of a web transport system having a nip roller and a receiving roller, as shown in Figure 10, the vibration source corresponds to the rotation frequency of the nip roller and its harmonics, and the rotation frequency of the receiving roller and its harmonics. The natural frequency corresponds to the natural frequency of each vibration mode of the nip roller alone, the natural frequency of each vibration mode of the receiving roller alone, the natural frequency of each vibration mode of the same phase of the nip system, and the natural frequency of each vibration mode of the opposite phase of the nip system. When any of these vibration sources and each natural frequency match or approach each other, a resonance phenomenon occurs. Therefore, in a web transport device having multiple rollers, there are multiple vibration sources and natural frequencies, so there is a high possibility that resonance will occur.

The method of determining the vibration mode is not particularly limited, but for example, in the case of a conveying system consisting of two rollers, a nip roller and a receiving roller, the determination can be made using the information on the measurement results of the roller runout at each measurement position and the flowchart shown in Figure 11. Note that Figure 11 shows the determination flow for vibration modes up to the second order for each of the four types of vibration modes.

The method of determining the vibration mode of the same phase of the nip system and the vibration mode of the opposite phase of the nip system is not particularly limited, but the following method can be used, for example. First, the vibration data of each roller measured as shown in FIG. 12 is Fourier transformed as shown in FIG. 13 and FIG. 14 to perform frequency analysis. Next, the frequency analysis results obtained as shown in FIG. 15 are compared to confirm the presence or absence of the same or nearby frequency components in each analysis result. If there are no same or nearby frequency components, it is determined that there is no resonance of the vibration mode of the same phase of the nip system or the opposite phase of the nip system. If there are same or nearby frequency components, it is determined that resonance of the vibration mode of the same phase of the nip system or the opposite phase of the nip system has occurred, and only the same or nearby frequency components are extracted as shown in FIG. 16, and reconverted into vibration data by inverse Fourier transform. At this time, if there are multiple same or nearby frequency components in both the nip roller and the receiving roller, the one with the smallest difference in frequency components between the nip roller and the receiving roller is the analysis target. The waveforms obtained for each roller are compared, and if the phases of the waveforms of the nip roller and the receiving roller are the same as shown in Figure 17, it is determined to be a nip system in-phase vibration mode, and if the phases of the waveforms of the nip roller and the receiving roller are opposite as shown in Figure 18, it is determined to be a nip system out-of-phase vibration mode.

The calculator 20 that identifies the vibration mode is not particularly limited, but as described above, it is preferable to use one that has the function of performing frequency analysis on the measured vibration data, comparing the obtained analysis data, and identifying the vibration mode based on a preset judgment flow. The hardware of the calculator 20 is not particularly limited, but it can be realized, for example, by using an information processing device equipped with a CPU, RAM, ROM, and various interfaces, or dedicated hardware. In addition, the form of communication from the vibration measuring device 13 installed on the roller to the vibration data transmission line 21 may be wired communication or wireless communication.

Here, assuming the technology of Patent Document 1, we will explain what can be learned from the vibration detection technology of the conventional technology. Figure 19 shows a schematic side view of a web conveying device having a nip roller 1 and a receiving roller 2, in which a vibration measuring device 13 is installed at the center of the longitudinal direction of the nip roller 1, as one embodiment of the conventional technology. In Figure 19, it is possible to detect resonance in odd-order vibration modes in which the center of the nip roller 1, which is the vibration measurement point, vibrates. Specifically, these are vibration modes such as the primary and tertiary vibration modes of the nip roller 1 alone, the same phase primary and tertiary vibration modes of the receiving nip system, and the opposite phase primary and tertiary vibration modes of the nip system. Also, when resonance occurs in the primary or tertiary vibration modes of the receiving roller 2 alone, the vibration of the receiving roller 2 is transmitted to the nip roller 1, and the resonance may be detected by a displacement meter installed on the nip roller 1.

On the other hand, in the case of FIG. 19, resonance of even-order vibration modes that do not cause displacement in the longitudinal center of the nip roller 1 may not be detectable. Specifically, these vibration modes include the second and fourth orders of the nip roller 1 alone, the second and fourth orders of the receiving roller 2 alone, the second and fourth orders of the same phase of the nip system, and the second and fourth orders of the opposite phase of the nip system. When resonance occurs in these even-order vibration modes, the polygonal phenomenon also occurs, so it is preferable to detect them in the same way as the odd-order vibration modes.

Here, FIG. 20 shows a conceptual diagram of an embodiment of the prior art in which, in the web conveying device of FIG. 19, when the web conveying speed is Am/min, the sixth harmonic of the nip roller is used as an excitation source, resonates with the natural frequency of one of the vibration modes, and then the web conveying speed is changed from Am/min to Bm/min to avoid resonance. As shown in FIG. 20, the rotational frequency and its harmonics of the nip roller and the receiving roller increase in proportion to the web conveying speed, but the natural frequency is a constant value independent of the web conveying speed. When the displacement of only the nip roller in the longitudinal center is measured, it is found that resonance occurs in an odd-order vibration mode at resonance 101, but it is impossible to determine which vibration mode resonance occurs in. In addition, when resonance is detected and the web conveying speed is changed from Am/min to Bm/min to avoid resonance 101, it is necessary to avoid resonance 102 even under the condition of Bm/min at the avoided destination. If resonance occurs in the nip system antiphase secondary vibration mode at a web transport speed of Bm/min, the center of the roller, where the displacement is measured, will not vibrate, and the occurrence of resonance will not be detected, leading to the occurrence of polygonal deformation.

In addition, FIG. 21 shows a conceptual diagram of another embodiment of the conventional technology in which, in the web conveying device of FIG. 19, when the web conveying speed is Am/min, the sixth harmonic of the nip roller is used as the excitation source, and resonance with the natural frequency of one of the vibration modes is achieved, and then the natural frequency of the conveying system is controlled to avoid resonance 101. In this case, too, resonance may occur again under the conditions where resonance 101 is avoided. Here, after controlling the natural frequency, it is assumed that the eighth harmonic of the nip roller is used as the excitation source, and resonance 103 of an odd-order vibration mode is detected. In this case, if resonance 103 is a vibration mode in phase with the nip system, the roller does not become polygonal even if the vibration increases, so there is no need to avoid resonance 103. On the other hand, if the displacement of the longitudinal center of only the nip roller is measured as in the conventional technology, it is impossible to distinguish the vibration mode, and it is impossible to determine whether it should be avoided or not. Furthermore, even if resonance 103 is avoided by changing the natural frequency or speed, new resonance may occur under the conditions where it is avoided.

In addition, if the vibration mode is not identified by simply measuring the vibration at the center of the roller as in the conventional technology, especially if the roller surface or coating has been polished or rewound, and the roller has not been used for long, the vibration may be small and the resonance may not be detected even if the odd-order vibration mode resonance occurs. Figure 22 shows a conceptual diagram of a typical web conveying device having a rubber-covered nip roller immediately after rewound, in which the sixth harmonic of the nip roller is used as the vibration source and the vibration at the center of the longitudinal direction of the nip roller is measured and frequency analysis is performed in a state where harmonic resonance of the first vibration mode in the opposite phase of the nip system occurs. As shown in Figure 22, even if resonance of the vibration mode in the opposite phase of the nip system occurs, if the roller has not been used for long, the intensity of the frequency of the harmonic of the vibration source is not outstanding compared to the intensity of other harmonics, and the occurrence of harmonic resonance may not be detected.

Harmonic resonance occurs over a long period of time, and once the polygonalization phenomenon of the roller occurs, the vibration increases, making it easy to detect the resonance. However, once the polygonalization phenomenon of the roller occurs, the surface unevenness of the roller surface becomes irreversibly and steadily more pronounced, so it is necessary to detect the occurrence of the resonance phenomenon in the vibration mode that leads to the polygonalization phenomenon at an early stage.

The inventors have discovered that, among the four vibration modes and orders mentioned above, when harmonic resonance occurs in the first order vibration mode of the antiphase of the nip system, the polygonal phenomenon occurs earliest.

The first order anti-phase vibration mode of the nip system is a vibration mode in which the two rollers vibrate in a bow shape in opposite directions, with the support position of the shaft as a node with no displacement, as shown in Figure 7. In order to identify the first order anti-phase vibration mode of the nip system from the four vibration modes and vibration modes of each order, it is sufficient to measure at least the vibration at the longitudinal center of each roller, where the displacement is greatest.

As a result of thorough research based on the above findings, it was found that it is possible to detect the nip system antiphase first vibration mode early by providing a vibration measuring device 13 that measures the longitudinal center position of each of the surfaces of two rollers that convey the web while clamping it, as shown in Figures 23 and 24, and calculating the measured vibration data.

Furthermore, if vibration measuring devices 13 are provided only at the longitudinal center of each of the two rollers, they will detect resonances of odd-order vibration modes of antiphase of the nip system, such as antiphase third-order vibration mode of the nip system and antiphase fifth-order vibration mode of the nip system, without distinction. However, it is possible to detect the antiphase first-order vibration mode of the nip system, which has the greatest effect on the polygonal phenomenon, without missing anything, so a great effect can be expected. In addition, since there is no particular limit to the number of vibration measuring devices 13 that can be installed, it is possible to accurately identify third-order or higher vibration modes by adding additional vibration measuring devices 13 in the longitudinal direction of the rollers.

The inventors also discovered that harmonic resonance is the second most likely to occur in the nip system antiphase second-order vibration mode.

As shown in Figure 25, the anti-phase secondary vibration mode of the nip system is a vibration mode in which two rollers vibrate in opposite directions, with the support position of the shaft and the longitudinal center of each roller as nodes with no displacement. In the anti-phase secondary vibration mode of the nip system, the displacement is maximum near positions 1/4 and 3/4 of the longitudinal length from the end of the roller, and there is no displacement at the longitudinal center, so it is sufficient to measure positions 1/4, 1/2, and 3/4 of the longitudinal length from at least one end of each roller.

As a result of careful study based on the above findings, it was found that, as shown in Figure 26, a vibration measuring device 13 is provided to measure positions 1/4, 1/2, and 3/4 of the longitudinal length of the surface of each of the two rollers that convey the web while clamping it, and by calculating the measured vibration data, it is possible to detect nip system antiphase secondary vibration modes early. As shown in Figure 26, the "end of the roller" in this application refers to the end of the roller shaft.

Furthermore, after the nip system antiphase second vibration mode, the vibration modes that are likely to cause harmonic resonance are the nip system antiphase third, nip system antiphase fourth, and nip system antiphase fifth, in that order. As mentioned above, there is no limit to the number of vibration measuring devices 13 that can be installed, and more vibration measuring devices 13 may be provided in order to detect vibration modes of the nip system antiphase third or higher.

Now, consider the case where the technology of the present invention is applied to a web conveying device having a nip roller 1 and a receiving roller 2 shown in FIG. 26. FIG. 27 shows a conceptual diagram of an embodiment of the present invention in which, in the web conveying device of FIG. 26, when the web conveying speed is Am/min, resonance of the first vibration mode of the antiphase of the nip system occurs with the sixth harmonic of the nip roller 1 as the excitation source, and then the web conveying speed is changed from Am/min to Bm/min to avoid resonance 101. By applying this technology, it is possible to identify the vibration mode at the time of resonance occurrence, and it is found that resonance 101 of the first vibration mode of the antiphase of the nip system, which leads to the polygonal phenomenon, occurs at the web conveying speed Am/min. It is also possible to detect the occurrence of a new resonance 102 of the second vibration mode of the antiphase of the nip system at the web conveying speed Bm/min, which is the destination of avoidance of resonance 101, and it is possible to determine that resonance 102 also needs to be avoided.

Figure 28 shows a conceptual diagram of one embodiment of the present invention in which, when the web transport speed is Am/min in the web transport device of Figure 26, the sixth harmonic of nip roller 1 is used as the excitation source, resonating with the natural frequency of one of the vibration modes, and then controlling the natural frequency of the transport system to avoid resonance 101. By applying this technology, it can be seen that before the natural frequency was controlled, resonance 101 of the nip system antiphase first vibration mode occurred. Furthermore, after the natural frequency was controlled, it can be seen that although resonance 103 occurred, the vibration mode was the nip system inphase first vibration mode, which does not lead to polygonization.

Furthermore, by identifying the vibration mode, it is possible to detect harmonic resonance even when the roller surface or coating is new or has only recently been used, such as immediately after polishing or rewinding, and the harmonic vibration components of the roller, which is the source of vibration, are weak.

As shown in FIG. 29, in the case of a web conveying device that uses two or more nip rollers 1 to clamp and convey a web with one receiving roller 2, harmonic resonance occurs between the receiving roller 2 and the nip roller 1, and between the receiving roller 1 and the second nip roller 15. Therefore, in the case of a web conveying device that uses two or more nip rollers 1 to clamp and convey a web, a vibration measuring device 13 is provided that measures the longitudinal center position of each of the surfaces of the two rollers that clamp and convey the web, and the measured vibration data is calculated to enable early detection of the nip system antiphase first vibration mode. In addition, the device detects resonance of odd-order vibration modes of the nip system antiphase, such as the nip system antiphase third vibration mode and the nip system antiphase fifth vibration mode, without distinction, but it is possible to detect the nip system antiphase first vibration mode, which has the greatest effect on the polygonal phenomenon, without missing any, so a great effect can be expected. In addition, since there is no particular limit to the number of vibration measuring devices 13 to be installed, it is possible to accurately identify third or higher vibration modes by separately adding vibration measuring devices 13 in the longitudinal direction of the roller.

In addition, when two or more nip rollers are used, a vibration measuring device 13 is provided to measure positions of 1/4, 1/2, and 3/4 of the longitudinal length from one end of the roller on the surface of each of the two rollers that convey the web while clamping it, and the measured vibration data is calculated, making it possible to detect the nip system antiphase second order vibration mode early. Note that after the nip system antiphase second order vibration mode, the vibration modes that are likely to cause harmonic resonance are the nip system antiphase third order, the nip system antiphase fourth order, and the nip system antiphase fifth order, in that order. As mentioned above, there is no limit to the number of vibration measuring devices 13 that can be installed, and more vibration measuring devices 13 may be provided in order to detect nip system antiphase third order or higher vibration modes.

In addition, in the case of a web conveying device in which the web is clamped and conveyed using a backup roller 16 that supports the nip roller 1 from behind the nip roller 1 as shown in FIG. 30, harmonic resonance also occurs between the nip roller 1 and the backup roller 16. Therefore, a vibration measuring device 13 is provided that measures the longitudinal center position of each surface of two rollers that contact without clamping the web, and the measured vibration data is calculated, making it possible to detect the first order vibration mode of the antiphase of the nip system early. In addition, the resonance of odd order vibration modes of the antiphase of the nip system, such as the third order vibration mode of the antiphase of the nip system and the fifth order vibration mode of the antiphase of the nip system, is also detected without distinction, but since the polygonal phenomenon occurs in both orders, there is no particular inconvenience due to the detection. In addition, since there is no particular limit to the number of vibration measuring devices 13 to be installed, it is possible to accurately identify third order or higher vibration modes by separately adding vibration measuring devices 13 in the longitudinal direction of the roller.

When a backup roller is used, a vibration measuring device 13 is provided to measure positions of 1/4, 1/2, and 3/4 of the longitudinal length from one end of the roller on the surface of each of the two rollers that contact the web without clamping it, and the measured vibration data is calculated to enable early detection of the nip system antiphase second order vibration mode. Note that after the nip system antiphase second order vibration mode, the vibration modes that are likely to cause harmonic resonance are the nip system antiphase third order, the nip system antiphase fourth order, and the nip system antiphase fifth order, in that order. As mentioned above, there is no limit to the number of vibration measuring devices 13 that can be installed, and more vibration measuring devices 13 may be provided in order to detect nip system antiphase third order or higher vibration modes.

In addition, even when a nip roller 1 and a backup roller are combined as in Figure 31, the above method can be used to quickly detect the vibration modes of the nip system antiphase primary and nip system antiphase secondary of two rollers that transport the web while clamping it, or two rollers that contact the web without clamping it.

Furthermore, after identifying the vibration mode using the above method, it is even more preferable to change the natural frequency of the conveying system, which makes it possible to avoid harmonic resonance. As a means for changing the natural frequency of the conveying system, a method in which the roller is made a water-permeable structure and the amount of liquid supplied is changed to change the weight of the roller, a method in which the temperature of the roller is changed, a method in which the weight of the roller is changed by attaching and removing weights to the shaft of the roller, a method in which the rigidity of the arm or frame is made adjustable to change the support rigidity, a method in which the support position of the roller is changed to change the distance between the fulcrums, and a method in which the pressing force of the nip roller is adjusted to control the amount of crushing of the rubber can be preferably used. Of these, the method of controlling the amount of crushing of the rubber by adjusting the pressing force of the nip roller, which does not require major equipment changes and can be easily adjusted during operation, can be preferably used. Furthermore, in order to prevent the deterioration of the surface pressure distribution due to the adjustment of the surface pressure, a roller having a double tube structure and a structure in which pressing is performed at the center can be preferably used.

Also, the change in the natural frequency of the conveying system requires some attention. Figure 32 shows a conceptual diagram showing the relationship between the speed and frequency of the rotational frequency and harmonics generated in a typical web conveying device. As shown in Figure 32, when the web conveying speed is constant, the harmonics of any one of the rollers constituting the conveying device exist at regular intervals. If the natural frequency of the conveying system is ω _EQ Hz and the rotational frequency of any one of the rollers constituting the conveying device is ω Hz, the harmonic resonance phenomenon occurs under the condition of ω _EQ /ω = N (N is a natural number). When the natural frequency of the conveying system is changed to avoid resonance after the occurrence of harmonic resonance, if the frequency is increased by the same frequency as the rotational frequency ωHz of the roller, (ω _EQ +ω) /ω = N + 1 = natural number, and harmonic resonance occurs at the avoided location. Similarly, even if the natural frequency of the conveying system is lowered by the rotational frequency ωHz of the roller after the occurrence of harmonic resonance, (ω _EQ -ω) /ω = N - 1 = natural number, and harmonic resonance still occurs. Therefore, in order to control the natural frequency of the transport system and avoid resonance, it is necessary to shift the natural frequency of the transport system by the amount of the rotation frequency that does not match the harmonic interval ω. In this case, since it is preferable for the natural frequency of the transport system to be as far away as possible from ω _EQ -ω, ω _{EQ, and} ω _EQ +ω, it is preferable to shift it by ω/2 Hz, which is half the value of ω. In this case, the natural frequency of the transport system may be increased or decreased by ω/2 Hz.

The following provides a more detailed explanation using examples, but the present invention is not limited to these examples. Measurement and evaluation methods are also described below.

[Vibration measurement method]
The vibration of the roller surface was constantly measured using a multi-color laser coaxial displacement meter CL-3050 manufactured by Keyence Corporation. The sampling frequency was 1 msec. The most recent one minute of measurement data was analyzed, and the amplitude was calculated by subtracting the minimum value from the maximum value of the waveform.

[Method of determining whether resonance occurs, and whether it is in phase or out of phase]
A conveying system consisting of two rollers, a receiving roller and a nip roller, will be described as an example. First, the vibration data of each roller measured as shown in FIG. 12 is subjected to frequency analysis as shown in FIG. 13 and FIG. 14. Next, the frequency analysis results obtained as shown in FIG. 15 are compared, and the presence or absence of a frequency component within 0.5 Hz is confirmed in each analysis result. Here, if there is no frequency component within 0.5 Hz, it is determined that no resonance occurs. Also, if there is a frequency component within 0.5 Hz, it is determined that resonance occurs, and only each frequency component within 0.5 Hz is extracted as shown in FIG. 16, and reconverted into vibration data by inverse Fourier transform. Here, the waveforms of each roller obtained are compared, and if the phases of the waveforms of the nip roller and the receiving roller are the same as shown in FIG. 17, it is determined that it is a vibration mode of the same phase, and if the phases of the waveforms of the nip roller and the receiving roller are opposite to each other as shown in FIG. 18, it is determined that it is a vibration mode of the opposite phase.

[Method of determining vibration mode]
The vibration mode was determined based on the flowchart shown in FIG.

[Test end decision]
In the measurement of the vibration amplitude, the conveying test was continued until the amplitude of any one of the laser displacement meters reached 200 μm or more, or until 365 days had elapsed.

[Surface shape measurement method]
First, a laser displacement meter LK-500 manufactured by Keyence Corporation was used to measure the surface shape at positions 1/4, 1/2, and 3/4 of the length from one end of the roller in the longitudinal direction while the roller was rotated at a speed of 1 m/min.

[Method of determining the number of sides for polygonization]
The data obtained by the surface shape measurement was subjected to frequency analysis, and the frequency of the peaks present excluding the rotation frequency of the roller was divided by the rotation frequency of the roller, and the nearest natural number to the value was determined as the number of sides of the polygon.

[Example 1]
A conveying device having a nip roller and a receiving roller as shown in FIG. 33 was used. The nip roller has a double tube structure, a diameter of φ330 mm, and a face length of 7000 mm. The nip roller has an EPDM rubber layer with a hardness of 50Hs JIS A (JIS K 6301-1995) on the surface. The receiving roller has a diameter of φ400 mm and a face length of 7000 mm. The receiving roller has an EPDM rubber layer with a hardness of 70Hs JIS A (JIS K 6301-1995) on the surface. Using the above-mentioned web conveying device, a polypropylene film with an average thickness of 5 μm and a width of 6000 mm was sandwiched and conveyed at a speed of 200 m/min with a wrap angle of 180 degrees. The surface pressure for sandwiching the film was 400 N/m. In addition, to detect the nip system anti-phase primary and secondary vibration modes, vibration measuring devices were placed on the surface of each roller at positions 1/4, 1/2, and 3/4 of the length from one end of the roller in the longitudinal direction.

[Example 2]
Except for using a nip roller having a double tube structure and a diameter of φ345 mm and a face length of 7000 mm, the web was transported in the same manner as in Example 1. By changing the roller, each natural frequency of the transport system changes from that of Example 1.

[Comparative Example 1]
The web was transported in the same manner as in Example 1, except that the vibration measuring device was disposed only at a position halfway along the longitudinal length of the nip rollers.

[Comparative Example 2]
The web was transported in the same manner as in Example 2, except that the vibration measuring device was disposed only at a position halfway along the longitudinal length of the nip rollers.

The results of the examples and comparative examples are shown in Table 1.

The relationship between speed and frequency in Comparative Example 1 is shown in Figure 34. In Comparative Example 1, 180 days after the start of the test, the amplitude at the center of the longitudinal direction of the nip roller exceeded 100 μm, and although the vibration mode was unknown, the occurrence of resonance 104 caused by the sixth harmonic of the nip roller as the vibration source was suggested. Therefore, in order to avoid resonance 104, the web conveying speed was changed from 200 m/min to 250 m/min. However, the vibration was not reduced even after the condition change, and 200 days after the start of the test, the amplitude at the center of the longitudinal direction of the nip roller exceeded 200 μm, and the test was discontinued. Measurement of the surface shape of the nip roller revealed that it had become hexagonal.

The relationship between speed and frequency in Example 1 is shown in FIG. 35. In Example 1, it was found that immediately after the start of the test, the transport system used the 6th harmonic of the nip roller as the excitation source, and resonance 104 occurred in the first vibration mode of the nip system inverse phase. Therefore, in order to avoid resonance 104, the web transport speed was changed from 200 m/min to 250 m/min. However, it was found that at a web transport speed of 250 m/min, resonance 105 occurred in the second vibration mode of the nip system inverse phase, with the 7th harmonic of the nip roller as the excitation source. Therefore, in order to also avoid resonance 105, the web transport speed was changed from 250 m/min to 270 m/min. No resonance was observed at a web transport speed of 270 m/min, and the amplitude of any vibration measuring device did not exceed 200 μm even after 365 days had passed since the start of the test. After the test was completed, the surface shape of the nip roller was measured, but no polygonal phenomenon had occurred.

Figure 36 shows the relationship between speed and frequency in Comparative Example 2. In Comparative Example 2, the amplitude at the center of the longitudinal direction of the nip roller did not exceed 100 μm even after 250 days had passed since the start of the test, but an abnormal noise was generated from the conveying device, and the test was abruptly stopped. Measurement of the surface shape of the nip roller revealed that it had become heptagonal, indicating that it was resonating.

The relationship between speed and frequency in Example 2 is shown in Figure 37. In Example 2, it was found that immediately after the start of the test, the conveying system used the seventh harmonic of the nip roller as the vibration source, and resonance 106 occurred in the nip system antiphase second vibration mode. Therefore, in order to avoid resonance 106, the surface pressure for clamping the film was changed from 400 N/m to 450 N/m. After the condition change, it was found that resonance 107 occurred in the nip system inphase first vibration mode, but this vibration mode did not develop into the polygonal phenomenon, so operation was continued as it was. Even after 365 days had passed since the start of the test, the amplitude of any vibration measuring device did not exceed 200 μm. After the test was completed, the surface shape of the nip roller was measured, but the polygonal phenomenon did not occur.

The present invention can be applied not only to nip rollers in film-making equipment, but also to press rollers in papermaking equipment and rolling rollers in ironmaking equipment, but the scope of application is not limited to these.

1: Nip roller 2: Receiving roller 3: Rubber layer of roller 4: Cylinder 5: Arm 6: Web 7: Bearing 10: Spring that connects rollers by regarding elastic bodies such as webs and rubber layers as springs 11: Displacement of nip roller 1 11': Displacement after half a period of displacement 11 of nip roller 1 12: Displacement of receiving roller 2 12': Displacement after half a period of displacement 12 of receiving roller 2 13: Vibration measuring device 14: Laser light 15: Second nip roller 16: Backup roller 20: Calculator 21 : Vibration data transmission line 101: Resonance in which the 6th harmonic of the nip roller is used as the excitation source, and the vibration occurs in the first vibration mode of the antiphase of the nip system 102: Resonance in which the 10th harmonic of the receiving roller is used as the excitation source, and the vibration occurs in the second vibration mode of the antiphase of the nip system 103: Resonance in which the 8th harmonic of the nip roller is used as the excitation source, and the vibration occurs in the first vibration mode of the in-phase of the nip system 104: Resonance in which the 6th harmonic of the nip roller is used as the excitation source, and the vibration occurs in the first vibration mode of the antiphase of the nip system 105: Resonance in which the 7th harmonic of the nip roller is used as the excitation source, and the vibration occurs in the second vibration mode of the antiphase of the nip system 106: Resonance in which the 7th harmonic of the nip roller is used as the excitation source, and the vibration occurs in the second vibration mode of the antiphase of the nip system 107: Resonance in which the 9th harmonic of the nip roller is used as the excitation source, and the vibration occurs in the first vibration mode of the in-phase of the nip system

Claims (6)

1. A method for predicting the occurrence of roller polygonization, comprising:
Identifying the vibration modes of the two rollers that convey the web while clamping it from vibration data obtained by measuring vibrations at the center positions in the longitudinal direction of the surfaces of the two rollers;
It is predicted that the two rollers will be polygonal when the two rollers are in a vibration mode that is in antiphase with each other.
A method for predicting the occurrence of roller polygonization phenomenon . 1. A method for predicting the occurrence of roller polygonization, comprising:
Identifying vibration modes of the two rollers from vibration data obtained by measuring vibrations at positions 1/4, 1/2, and 3/4 of the longitudinal length from one end of the rollers on the surfaces of the two rollers that convey the web while clamping the web;
It is predicted that the two rollers will be polygonal when the two rollers are in anti-phase vibration modes with each other.
A method for predicting the occurrence of roller polygonization phenomenon . 1. A method for predicting the occurrence of roller polygonization, comprising:
identifying a vibration mode of the two rollers that are in contact with the web without clamping it, from vibration data obtained by measuring vibration at a longitudinal center position on the surface of one of the two rollers that convey the web while clamping it, and a roller that is in contact with the one roller without clamping the web, and
When two rollers in contact with the web without pinching it are in anti-phase vibration modes, the two rollers are predicted to be polygonal.
A method for predicting the occurrence of roller polygonization phenomenon . 1. A method for predicting the occurrence of roller polygonization, comprising:
identifying vibration modes of the two rollers in contact with the one roller without clamping the web from vibration data measured at positions 1/4, 1/2, and 3/4 of the longitudinal length from one end of the roller on the surface of each of the two rollers that convey the web while clamping it, and
When two rollers in contact with the web without pinching it are in anti-phase vibration modes, the two rollers are predicted to be polygonal.
A method for predicting the occurrence of roller polygonization phenomenon . a conveying system including at least two rollers for conveying the web while pinching it, and a support for rotatably supporting the two rollers;
A method for changing the natural frequency of a conveying system, comprising: changing the natural frequency of the entire conveying system when it is predicted that a roller will become polygonal by the method for predicting the occurrence of the roller polygonal phenomenon according to any one of claims 1 to 4. 6. The method for changing the natural frequency of a conveyance system according to claim 5 , further comprising changing the natural frequency of the conveyance system by ω/2 [Hz].
however,
ω=V/(D·π)
ω: Rotation frequency of one of the rollers from which vibration data was obtained [Hz]
V: web transport speed [m/sec]
D: diameter of any one of the rollers from which vibration data was obtained [m]

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