JP3437602B2 - Method and device for suppressing self-excited vibration in fluid levitation device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a plurality of jet ports (or slits) or at least one jet port (or slit) having a closed curve, and air or nitrogen is supplied from the jet ports (or slits). A fluid levitation device (hereinafter referred to as an air curtain type) that ejects a compressible fluid and generates a pressure between the levitation object and the levitation device by the curtain sealing effect of the fluid to levitate the object, such as a strip steel plate The present invention relates to a fluid levitation device that floats and conveys fluid, and a fluid levitation device (hereinafter referred to as a pocket type) that is used for high-speed mechanical bearings and that includes a jet port (or slit) and a pocket that generates pressure. It is intended to improve the stability of self-excited vibration of such a fluid levitation device.

[0002]

2. Description of the Related Art With the demand for high surface quality of strip-shaped products, attention has been paid to a fluid levitation device that can convey the strip-shaped products in a non-contact manner. Also, in supporting a high-speed rotating shaft of a machine, it solves problems of accuracy and friction. For this reason, a fluid levitation device called a hydrostatic bearing is widely used.

FIG. 7 is a cross-sectional view showing an example of a known air curtain type fluid levitation device. The compressive fluid sent to the header B from a compressible fluid supply source device (not shown) is a nozzle slit. Gush from 1a, 1b,
A region A sandwiched between the nozzle slits 1a and 1b by colliding with the floating object 10 and changing its direction, and this momentum change.
A pressure is generated in the part to levitate the levitated object 10. The balance of the portion generating the levitation pressure is, for example, the levitation object 1
0 is subject to disturbances such as fluctuations in tension on the strip-shaped steel sheet and the like, and the pressure source of the compressible fluid is inevitably subject to small pressure fluctuations. Therefore, these disturbances may cause self-excited vibration. Yes, and if this happens, it cannot be transported normally. Currently, the countermeasures against this are to change the levitation conditions and the operating conditions of the line empirically, and to add a device for damping vibrations in the strip steel sheet conveyance line to prevent obstacles in the conveyance of strip steel sheets. The reality is that the generation of vibration is suppressed to the extent that it does not occur.

FIG. 8 is a sectional view showing an example of a well-known pocket type fluid levitation device, in which the resistance when flowing out from the pocket portion A generates pressure in the pocket portion A. The floating object 10 (for example, the rotation axis)
To support levitation. This example is published in P. 32 of the Japan Society of Mechanical Engineers (Part 3) Vol. 187
7 is a diagram in which the research results of the vibration stabilizing element by Mori et al. Shown in Nos. 7 to 1882 are inserted. As shown in this document, vibration can be stabilized by providing a fluid resistance element and a stabilizing chamber D in a portion connected to the bearing pocket A, but the method of the document provides an air curtain type fluid levitation device. Is not applicable, and the manufacturing process of the stabilization chamber D is difficult due to the location, and a device needs to be devised.

Further, as seen in Japanese Patent Publication No. 3-249423, Japanese Patent Publication No. 3-249424, etc., in a pocket type static pressure bearing, it is necessary to reduce the pocket volume while securing the area of the pressure receiving portion. Therefore, there are inventions that improve the stability of self-excited vibration and other characteristics, but in the air curtain type fluid levitation device,
Originally, the structure has only a pocket volume equivalent to the flying height, and therefore no margin for stability improvement can be expected by these methods.

[0006]

As described above, in a device for levitating an object by generating a pressure between the levitating object and the levitating device by supplying the compressive fluid, the self-excited vibration of the compressible fluid is generated. Suppression is an important issue. The conventional vibration suppression measures used in the air curtain type fluid levitation system require a great deal of labor to search for stable operating conditions and also cause operational restrictions, and increase the margin of the compressive fluid supply device. Since it had to be taken, much energy wasted. In addition, in the method of suppressing the occurrence of vibration by adding a device for damping the vibration in the transfer line, it is necessary to provide a device for this purpose, and since an extra tension is added, the operation is performed. However, there is a problem that it cannot be used as a levitation device that conveys a thin strip-shaped product having a wide width.

On the other hand, the vibration suppression measures in the pocket type levitation device cannot be applied to the air curtain type fluid levitation device and are difficult to process. Moreover, the floating object is not a machined product but a large one such as a steel plate. However, the application effect was insufficient for those with poor levitation clearance dimension accuracy.

[0008]

Therefore, the present inventors have
By analyzing the vibration characteristics of the fluid balance of the fluid levitation device and experimentally elucidating the vibration characteristics, the following was found. A self-excited vibration suppressing method in a fluid levitation device of the present invention is a method of ejecting a fluid from a plurality of ejection ports (or slits) communicating with a supply source of a compressive fluid or a plurality of closed curve ejection ports (or slits). The area between the jets (or slits) from which the fluid is jetted, or the jets (or slits) that form a closed curve
A method for suppressing self-excited vibration in a fluid levitation device that levitates an object by generating a static pressure between the object and a floating object in a region surrounded by The object is levitated without injecting the compressive fluid from the ejection contour (or slit) that is inside the levitation width and is closest to the outer contour of the levitation body or the levitation width of the levitation body. The outer contour or the floating object
The jet (or slit) closest to the ascent width and its head
Characterized Rukoto allowed the role of the pressure introducing hole and the pressure accumulation chamber Zehnder.

Further, the self-excited vibration suppressing device in the fluid levitation device of the present invention has a plurality of jet ports (or slits) communicating with the supply source of the compressible fluid, or a jet port (or slit) having a plurality of closed curves. In a region surrounded by the ejection ports (or slits) having a closed curve and ejecting the fluid from the ejection ports (or slits) and ejecting the fluid. A device for suppressing self-excited vibration of a floating object in a fluid levitation device that generates static pressure between the floating object and the floating object, and is outside the floating object from a jet port (or slit) from which the fluid is ejected. And a pressure conducting hole (or slit) that conducts to the
And a pressure accumulation chamber for taking in and releasing through

Further, at the jet outlet (or slit) communicating with the supply source of the compressive fluid and the fluid jet position,
The same applies to a device that suppresses self-excited vibration of a floating object in a fluid levitation device that is composed of a pocket that generates a static pressure by the ejected fluid and that generates a static pressure between the floating object and the floating object. That is, it is composed of a pressure conduction hole (or slit) that conducts to the outside of the floating object from the end of the pocket that generates static pressure, and a pressure accumulation chamber that takes in and releases the compressive fluid through the conduction hole (or slit). It is characterized by that.

That is, in an air curtain type fluid levitation device, a pressure communicating hole from the ejection port (or slit) for generating pressure in the levitation gap portion to the outer end side of the levitation object and its pressure accumulating chamber are provided, or In a pocket-type fluid levitation device, self-excitation is performed by utilizing the fact that the stability of vibration is increased by providing a pressure conduction hole from the pocket end that creates pressure to the outer end side of the floating object and its pressure accumulation chamber. This is to suppress vibration, and in a fluid levitation device with multiple jets (or slits), by stopping the levitation jet from the jets (or slits) near the edge of the floating object, the header of this jet system is Method for making the role of pressure accumulating chamber and / or pressure accumulating chamber and pressure communicating hole (or slit) for suppressing self-excited vibration
Is provided. The compressible fluid here corresponds to a gas body such as air.

[0012]

In the levitation method and apparatus of the present invention configured as described above, when the levitation amount of the levitation object fluctuates due to some disturbance, the change in the flow rate flowing through the levitation gap portion causes the mass of the fluid stored in the accumulation chamber to change. Can be compensated. In other words, if there is a storage chamber connected to the flow rate in the floating gap, the integration (accumulation) effect of the change in flow rate will appear significantly with respect to the height change. It means a large value, and a general equation of motion of vibration m (dx ² / dt ² ) + c (dx / dt) + kx = F m: vibration mass c: viscous damping coefficient k: spring constant F: disturbance x: vibration displacement This is equivalent to the fact that the viscous damping term c is large, and the stability against vibration increases.

Further, the vibration stabilization by this action is a method of compensating for the change in the flow rate flowing through the floating gap portion, so that it can be applied to both the air curtain type fluid levitation device and the pocket type fluid levitation device. Since the coefficient corresponding to the viscous damping term is increased, the vibration stabilizing effect is large, and it is easy to quantitatively select it by setting the volume.

[0014]

Embodiments will be described in detail below with reference to the drawings. The configuration for suppressing vibration is the same for both the air curtain type fluid levitation device and the pocket type fluid levitation device. Therefore, in order to facilitate the description, the description will be given mainly on the air curtain type fluid levitation device.

FIG. 1 is a sectional view of a first embodiment of a fluid levitation apparatus according to the present invention. The fluid sent from a compressive fluid supply source (not shown) enters the header chamber B, is ejected from the ejection slits 1a and 1b, generates pressure in the portion A, and flows out from the floating gap portion. The slits 2a and 2b are connected to the storage chambers Ca and Cb as the pressure conducting holes of the outflow portion,
Balance pressure is stored in the storage chamber. The conduction holes 3a and 3b for connecting the storage chambers Ca and Cb to the outside are not always necessary, but it is also effective to provide them if control of the balance pressure of the storage chambers Ca and Cb is required.

When the flying height of the floating object 10, that is, the floating clearance changes due to some disturbance from such a balanced state, the flow state of the floating clearance changes, and the flow rate is absorbed by the gas mass in the storage chamber C accordingly. , Is discharged via the conduction holes 2a and 2b, and a damping effect for fluctuations in the flying height is produced. FIG. 2 is a sectional view of a second embodiment of the fluid levitation device of the present invention, in which the present invention is applied to a general pocket type static pressure bearing used when the levitation gap is small. This is the same as the first embodiment except that a pocket having a narrowed inlet is used to generate a pressure in the portion A, and the conduction hole slits 2a and 2b and the accumulation chambers Ca and Cb are used for suppressing vibration.
Is also provided as in the first embodiment. FIG. 3 is a bird's-eye view of the first embodiment of the present invention shown in FIG. 1, and shows an example of a levitation carrier device in which the levitation object 10 is a strip steel plate and conveys while turning 180 degrees.

FIG. 4 shows the result of an experimental investigation on the effect of the present invention. It is the result of an experiment conducted by placing a plate width of 1 m and a load of 60 kg on a levitation device that turns 180 degrees at a radius of 1.2 m.
Compared to FIG. 4 (a) which does not have a storage chamber of the present invention, it is about 0.3 m ³
In FIG. 4 (b) in which the storage chamber C of the present invention is provided, there is almost no vibration other than a slight pressure fluctuation due to the air flow,
Also, it can be seen that even if it occurs a little, it is immediately attenuated.

FIG. 5 shows a change in the vibration suppressing effect according to the volume of the storage chamber C of the present invention, and is a calculation result when the plate width of the levitation device with the 180-degree turn is 1 m and the load is 130 kg. Even with such a large load, if the volume of the storage chamber C is set to about 0.3 m ³ , it is possible to escape from the vibration generation region, and if it is set to a large volume, the margin for vibration generation can be rapidly increased. I understand. Although the storage chambers C may be provided asymmetrically in terms of vibration suppression, it is generally preferable to provide the storage chambers C symmetrically because the floating characteristics are slightly changed by providing the storage chamber C.

The conducting paths 2a, 2b of the accumulating chamber are located outside the nozzle slits 1a, 1b, that is, on the outer end side of the floating object 10, in the floating gap area (the area sandwiched between the floating object 10 and the floating pad 11). ) Is preferable, but
Even if it is out of the floating gap region, it is effective if it is in a region that compensates for the flow rate change in the floating gap portion. That is, the flow in the levitation gap portion flows along the pad 11 even if it is separated from the outer end of the levitation object 10. Therefore, even if it is outside the end of the levitation object 10, there is a flow rate change compensation capability, and experimentally, Has a vibration suppressing effect even when the positions of the conduction holes 2a and 2b are separated from the outside of the floating object 10 up to a position 3 to 4 times the floating gap amount. Although the storage chamber C is provided on the floating pad 11 side in the embodiments of FIGS. 1 and 2, if the floating object 10 is a solid volume such as a shaft, pressure accumulation on the floating object 10 side. The chamber C and the pressure communication path 2 may be provided.

FIG. 6 shows a floating object 10 from a plurality of ejection ports.
The method of the present invention is applied to a fluid levitation device that selectively uses jets according to the size of
The header B ₂ close to the end 10 of the floating object and the flow rate control valve 32 connected to the jet port are closed, and the jetting of the fluid for levitation is performed by opening the flow rate control valve 31 (from the header B ₂ and its jet port). ) It is done by the header B _{1 on the} inside and its jet. By adopting this method, the header B ₂ and its ejection port serve as the pressure accumulating chamber and the pressure communicating hole , and the same self-excited vibration suppressing effect as described above is exhibited. It should be noted that although two systems of ejection ports (or slits) are used in the present embodiment for ease of explanation, the present invention is also applicable to those having more ejection ports (or slits). It goes without saying that the invention can also be applied to a structure in which the jet headers B ₁ and B ₂ are independent left and right, and the left and right flow rate balance can be adjusted.

[0021]

As described above, according to the present invention, whether an air curtain type fluid levitation device or a pocket type fluid levitation device is provided, an extra device is added and the energy margin of a large compressible fluid supply source is increased. It is possible to achieve a stable fluid levitation device in which self-excited vibration due to a compressible fluid does not easily occur without having it, and it is easy to process and its application effect is very large.

[Brief description of drawings]

FIG. 1 is a diagram of a first embodiment of the present invention in an air curtain type fluid levitation device.

FIG. 2 is a second embodiment of the present invention in a pocket type fluid levitation device.

FIG. 3 is a bird's eye view in the first embodiment of the present invention.

FIG. 4 is a comparison diagram of measurement results of vibration waveforms with and without the present invention.

FIG. 5 is a diagram showing a volume of a storage chamber and a vibration stabilizing effect of the present invention.

FIG. 6 is an explanatory diagram in which the method of the present invention is applied when a jet port is selectively used from among a plurality of jet ports according to the size of the floating object 10.

FIG. 7 is a sectional view of a conventional fluid levitation device.

FIG. 8 is a sectional view of a conventional fluid levitation device.

[Explanation of symbols]

A Pressure generator B header room C storage room 1a, 1b Ejection slit 2a, 2b Pressure conduit 10 Levitating object 11 Fluid levitation device 31, 32 Flow control valve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI F16C 32/06 F16C 32/06 A // C21D 9/63 C21D 9/63 (58) Fields investigated (Int.Cl. ⁷ , DB name) B65G 7/06 B65H 5/22 B65H 20/14 B65H 23/32 B65H 29/24 F16C 32/06

Claims (3)

(57) [Claims] 1. A jet port (or a jet port) from which a fluid is jetted by jetting the fluid from a plurality of jet ports (or slits) communicating with a supply source of a compressible fluid or jet ports (or slits) forming a plurality of closed curves. Self-excited vibration in a fluid levitation device that levitates an object by creating a static pressure between it and the floating object in the area sandwiched by slits or in the area surrounded by the jet (or slit) consisting of a closed curve. A method of suppressing the jet, which is inside the outer contour of the levitating object or the flying width of the levitating object and is closest to the outer contour of the levitating object or the levitating width of the levitating object (or slit). Located inside without ejecting compressible fluid from
An object is levitated by the header and its ejection port (or slit) , and the outer contour of the levitated object or the levitated object is floated.
Outlet (or slit) closest to top width and its header
Self-excited vibration suppression method in a fluid levitation apparatus according to claim Rukoto allowed the role of the pressure introducing hole and the pressure accumulation chamber over. 2. A plurality of jet ports (or slits) communicating with a supply source of a compressive fluid, or a jet port (or slit) having a plurality of closed curves, and the fluid is discharged from the jet ports (or slits). Generate static pressure between the floating object and the area between the jets (or slits) where the fluid is jetted out, or the area surrounded by the jets (or slits) that are closed curves. A device for suppressing self-excited vibration of a floating object in a fluid levitation device that levitates an object, and a pressure communicating hole (or slit) that conducts to the outside of the floating object from a jet port (or slit) from which fluid is ejected, and compressibility Fluid through the conduction hole (or slit)
A self-excited vibration suppression device in a fluid levitation device, which comprises a pressure accumulation chamber that is taken in and released through 3. A jet port (or slit) communicating with a supply source of a compressive fluid, and a pocket at the fluid jetting position for generating static pressure by the jetting fluid, and between the jetting body and the floating object. A device for suppressing self-excited vibration of a floating object in a fluid levitation device for generating a static pressure to levitate the object, the pressure-conducting hole (or slit) communicating from the end of the pocket that generates the static pressure to the outside of the floating object. And a pressure accumulation chamber for taking in and discharging a compressive fluid through the communicating hole (or slit), and a self-excited vibration suppressing device in a fluid levitation device.