JPH06305526A - Fluid floating device - Google Patents

Abstract

PURPOSE:To provide a fluid floating device excellent in fluid floating stability by way of restraining generation of self-excited oscillation by compressible fluid by providing a pressure continuity hole to continue from a storage chamber to the side of a floating object on a guide as well as providing the pressure storage chamber in the guide. CONSTITUTION:Fluid delivered from a compressible fluid supply source enters a header chamber B, is exhausted from exhaust slits 1a and 1b, generates static pressure and flows out from a clearance part. Pressure of this flowout part is led to storage chambers Ca, Cb provided on guides 12a, 12b by continuity slits 2a, 2b, and balance pressure is stored in the storage chamber C. When the floating amount, that is, a floating clearance of a floating object 10 changes from such a balanced state due to some disturbance, the flowing state of the floating clearance part changes, accordingly absorption and bleedoff of a flow rate are carried out through the continuity slits 2a, 2b by a gas of mass the storage chamber C, and a damping effect against change of the floating amount is made. Continuity slits 3a, 3b control balance pressure of the storage chamber C.

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 closed curve jet port (or slit), from which air or nitrogen is discharged. A fluid levitation device (hereinafter referred to as an air curtain type) that blasts a compressible fluid such as, and creates a static pressure between the levitation object and the levitation device due to the curtain sealing effect of the fluid, for example, a strip shape. Fluid levitation device that floats and conveys steel sheets, etc., and a fluid levitation device that is used for high-speed mechanical bearings and that consists of jet ports (or slits) and pockets that generate static pressure (hereinafter referred to as pocket type ), It improves the stability of self-excited vibration of a floating object in 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 has been widely used.

FIG. 5 is a cross-sectional view of an example of a known air curtain type fluid levitation device. The compressible fluid sent to the header B from a compressible fluid supply source device (not shown) is the nozzle slit 1a, It jets from 1b, collides with the levitating object 10 and changes its direction, and due to this momentum change, a static pressure is generated in the area A sandwiched between the nozzle slits 1a and 1b to levitate the levitating object 10. The balance of the portion generating the floating static pressure is, for example, the floating object 10
The strip-shaped steel sheet conveyed by the machine is subject to external disturbances such as tension fluctuations, and the pressure source of the compressible fluid is also inevitably subject to minute pressure fluctuations.Therefore, these disturbances may cause self-excited vibrations. However, if this happens, normal transportation cannot be performed. Currently, as countermeasures against this, levitation conditions and line operating conditions are empirically changed, and a device for vibration damping is added to the strip steel sheet conveyance line to prevent obstacles to the conveyance of strip steel sheets. The actual situation is that the generation of vibration is suppressed to some extent.

FIG. 6 is a sectional view showing an example of a well-known pocket type fluid levitation device, in which the resistance when flowing away from the pocket portion A causes static pressure in the pocket portion A, As a result, the floating object 10 (for example, the rotation axis)
To support levitation. This example is from the Japan Society of Mechanical Engineers (Part 3) Volume 32, No. 244 (Sho 41.12) P. 1877-18
The results of the research on the vibration stabilizing element by Mori et al. 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. However, 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.

On the other hand, as seen in Japanese Examined Patent Publication No. 3-249423 and Japanese Examined Patent Publication No. 3-249424, in a pocket type static pressure bearing, the pocket volume is reduced while ensuring the area of the pressure receiving portion. Therefore, there are inventions that improve the stability of self-excited vibration and other characteristics, but since the air curtain type fluid levitation device originally has a pocket volume equivalent to the levitation height, these The method cannot improve the stability.

[0006]

As described above, in a device that levitates an object by generating a static pressure between the levitating object and the levitating device by supplying the compressive fluid, self-excited vibration caused by the compressible fluid. The suppression of 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.

It is an object of the present invention to provide a fluid levitation device which focuses on a fluid levitation device having guides outside both ends of a levitation object and which suppresses the occurrence of self-excited vibration and improves the fluid levitation stability.

[0009]

Therefore, the present inventor has found the following by analyzing the fluid balance and vibration characteristics of the fluid levitation device and experimentally clarifying the vibration characteristics. The present invention has a plurality of ejection ports (or slits) communicating with a supply source of a compressive fluid, or at least one ejection port (or slit) forming a closed curve, and the fluid is ejected from the ejection ports (or slits). Static pressure is generated between the floating object and the area between a pair of jets (or slits) from which the fluid is jetted, or the area surrounded by jets (or slits) that form a closed curve. In the fluid levitation device, in which the object is levitated and the lateral deviation of the levitation object is suppressed by the guides on the both outer sides of the levitation object, a pressure accumulating chamber is provided in the guide, and the guide is provided on the levitation object side. It is characterized in that a pressure conducting hole or a slit for conducting to is provided.

In addition, at the jet outlet or jet slit and the fluid jet position, which communicates with the supply source of the compressive fluid,
It consists of a pocket that generates static pressure by the ejected fluid and generates static pressure between it and a floating object to levitate it, and guides located outside both ends of the floating object suppress lateral deflection of the floating object. The same applies to the fluid levitation device. That is, a jet slit of an air curtain type fluid levitation device that generates static pressure in the levitation gap,
Alternatively, by providing a guide for the floating object from the pocket end that creates the static pressure of the pocket-type fluid levitation device, and providing a storage chamber in this guide that communicates with the fluid flowing through the levitation gap through the pressure communication hole, Vibration is suppressed by utilizing the fact that the stability of vibration in the levitation device is increased. The compressible fluid here corresponds to a gas body such as air.

[0011]

In the levitation device of the present invention configured as described above, when the levitation amount of the levitation object fluctuates due to some disturbance,
The mass of the fluid stored in the storage chamber can compensate for the change in the flow rate flowing through the floating gap. In other words, the fact that there is a storage chamber that leads to the flow rate in the floating gap part
The integral (accumulation) effect of the change in the flow rate appears significantly, which means that the first-order lag element with respect to the height variation is large, and the general equation of motion m (dx ² / dt ² ) + c ( dx / dt) + kx = F However, m: vibrating mass c: viscous damping coefficient k: spring constant F: disturbance x: viscous divisor term of vibration displacement is equivalent to large c, and stability against vibration increases.

Further, the vibration stabilization due to 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 an air curtain type fluid levitation device and a 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.

[0013]

Embodiments will be described in detail below with reference to the drawings. Since the air curtain type fluid levitation device and the pocket type fluid levitation device have the same vibration suppressing configuration, the description will be given mainly on the air curtain type fluid levitation device for ease of explanation.

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 jetted from the jet slits 1a and 1b, generates a static pressure in the portion A, and flows out from the gap portion to the outside. The pressure at the outflow portion is guided by the conduction slits (or holes) 2a, 2b to guides 12a, 12b.
The balance pressure is led to the accumulating chambers Ca and Cb provided in the storage chamber, and the balance pressure is stored in the accumulating chamber. Although the conduction holes 3a and 3b for connecting the storage chambers Ca and Cb to the outside are not always necessary,
If control of the balance pressure of Cb is required, it is effective to provide this.

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. In FIG. 1, the guides 12a and 12b have a structure that can be moved by a drive device (not shown) in response to the dimensional change of the floating object 10. The right half is the left half when the floating object 10-1 is large. Indicates a case where the floating object 10-2 is small.

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. is there. This is the same as the first embodiment except that a pocket with a narrowed inlet is used to generate a static pressure in the portion A. Due to vibration, the through hole slits 2a and 2b and the storage chamber C are used.
Also, a and Cb are provided as in the first embodiment.

The results of an experimental investigation on the effect of the present invention are shown in FIG. FIG. 3 is a result of an experiment conducted by mounting a plate width of 1 m and a load of 60 kg on a levitation device that turns 180 degrees shown in FIG. 7 with a radius of 1.2 m, but compared with FIG.
In FIG. 3 (b) in which the accumulating chamber C of the present invention of about 0.3 m ³ is provided, almost no vibration occurs except for a slight pressure fluctuation due to the air flow, and even if it occurs a little, it is immediately attenuated. You can see that

FIG. 4 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 at a plate width of 1 m and a load of 130 kg of the levitation device of the above 180 degree turn. 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. Even in the levitation device of the type shown in FIG. 2, the vibration suppression effect of the storage chamber provided in the guide has the same tendency as in FIG. In addition, the storage chamber C is asymmetrical in terms of vibration suppression.
However, since the levitation characteristics are slightly changed by providing the storage chamber C, it is generally preferable to provide the storage chamber C symmetrically.

Further, in the fluid levitation device or the like used in the belt-like material conveying device as in the example of FIG. 7, the guide is not provided all around, but only in the width direction or in a part thereof. Even if the present invention is applied, it is effective. Further, if the conduction paths 2a, 2b of the accumulation chamber are located on the outflow side of the nozzle slits 1a, 1b, that is, in the guide provided on the outer end side of the floating object 10, the flow rate change of the floating gap portion flowing along the flow path 2a, 2b can be suppressed. Since the effect of vibration compensation can be achieved by compensating, the arrangement (height, etc.) of the conducting paths 2a, 2b of the accumulating chamber is appropriately determined according to the desired flying height, etc., and is not necessarily limited to the lower end. As a levitating object which is symmetrical with respect to, a steel plate, a mechanical shaft, an aluminum plate, or the like does not change its action.

[0020]

As described above, according to the present invention, in both an air curtain type fluid levitation device and a pocket type fluid levitation device, a floating object of a floating object can be obtained without a large energy margin of the compressive fluid supply source. It is possible to achieve a stable fluid levitation device that is easy to handle when the dimensions change and is easy to process, and which is less likely to generate self-excited vibration due to a compressive fluid. It is possible to achieve stability, and its application effect is very large.

[Brief description of drawings]

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

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

FIG. 3 is a comparison diagram of measurement results of vibration waveforms with and without the present invention.

FIG. 4 is a diagram showing a volume of a storage chamber and a vibration stabilizing effect of the present invention.

FIG. 5 is a cross-sectional view of a conventional fluid levitation device.

FIG. 6 is a cross-sectional view of another conventional fluid levitation device.

FIG. 7 is a bird's-eye view showing the state of a fluid levitation device with a 180-degree turn, which is used to convey a belt-like material.

[Explanation of symbols]

 A static pressure generation part B header chamber Ca, Cb storage chamber 1a, 1b ejection slits 2a, 2b storage chamber conduction path 10 floating object 11 fluid levitation device

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B65H 29/24 A C21D 9/63 F16C 32/06 Z 8613-3J

Claims (2)

[Claims] 1. A plurality of jet outlets (or slits) communicating with a supply source of a compressive fluid, or at least one jet outlet (or slit) forming a closed curve, and from the jet outlets (or slits) Static pressure is applied to the floating object in the area sandwiched by a pair of jets (or slits) that ejects the fluid and ejects the fluid, or in the area surrounded by the jets (or slits) that form a closed curve. In a fluid levitation device that generates and levitates an object and suppresses lateral shake of the levitating object by guides located outside both ends of the levitating object, a pressure accumulating chamber is provided in the guide, and the object is levitated from the accumulating chamber A fluid levitation device, characterized in that a pressure conducting hole or slit is provided on the side thereof for conducting. 2. A jet nozzle or a jet slit which communicates with a supply source of a compressive fluid, and a pocket which is located at the jet position of the fluid and generates a static pressure by the jetting fluid. In a fluid levitation device that generates pressure to levitate the object and suppresses lateral deviation of the levitating object by guides located on both outer sides of the levitating object, a pressure accumulating chamber is provided in the guide, and the accumulating is performed in the guide. A fluid levitation device, characterized in that a pressure conducting hole or slit is provided for conducting from the chamber to the floating object side.