JPH06307448A - Porous static pressure bearing and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a static pressure bearing which has a low flow amount, high rigidity, high speed, and high accuracy by forming a fluid passage in the static pressure bearing with ceramic and using a porous material in the fluid passage. CONSTITUTION:In a static pressure bearing for floating up it in non contact condition by supplying fluid in space provided between solids, the shaft space outlet 17 and diameter space outlet 18 of a porous 16 are formed as a ceramic made porous static pressure bearing formed in such constitution that small diameter particles are embedded and fixed by a binder.

Description

Detailed Description of the Invention

[0001]

[Industrial application] As a means for increasing the smoothness and precision of relative motion between solids and maintaining it for a long time, a fluid such as oil or air is supplied under pressure between solids so that the solids can be moved between solids. There is a fluid lubrication that causes non-contact levitation. An example of this is a hydrostatic bearing in which a high-pressure fluid is supplied between solids, that is, a gap between a shaft and a bearing to float in a non-contact manner. As an example of a method of supplying a fluid to a minute gap between a shaft and a bearing in a hydrostatic bearing, there is a method of forming one of the shaft and the bearing with a porous body. This hydrostatic bearing is characterized in that the porous body also serves as a fluid passage and a throttle. The present invention relates to a structure and a manufacturing method of a passage and a throttle of a porous body in a hydrostatic bearing using the porous body.

[0002]

2. Description of the Related Art As a porous body material for a porous hydrostatic bearing, a porous body produced by sintering powder of metal, carbon (graphite), ceramics or the like is used. Only the carbonaceous porous material is present, and other materials can be said to be at the research level. Further, even with a carbonaceous porous body, the applicable fluid is gas (usually air), and it can be said that the porous hydrostatic bearing itself is a developing technology. FIG. 5 is a cross-sectional view showing an example of a conventional hydrostatic bearing using a carbonaceous porous material, where 1 is a hollow cylindrical shaft that serves as a rotating shaft, and 2 is a cylindrical porous carbonaceous material that serves as a bearing. The body, and 3 are face plates connected to both sides of the hollow shaft 1. 4 is a minute diameter gap formed in the radial direction between the hollow shaft 1 and the carbonaceous porous body 2, similarly 5 is an axial gap formed in the axial direction between the face plate 3 and the carbonaceous porous body 2, and 6 is carbon. The case for holding the porous carbon body 2, 7 is an air supply hole for penetrating the case 6 to allow compressed air to pass through the porous carbon body 2, and 8 is an air supply groove provided on the outer circumference of the cylinder of the porous carbon body 2. , 9 are radial clearance 4 and axial clearance 5
It is an exhaust port for independent supply of air to the space.

The function of the hydrostatic bearing will be described below.
The compressed air supplied from the air supply hole 7 passes through the carbonaceous porous body 2 through the air supply groove 8, flows through the radial gap 4 and the axial gap 5, and is then released into the atmosphere. The pressure of compressed air is 8
Although the inside is the same, it is once reduced by the flow path resistance in the carbonaceous porous body 2 and then receives the flow path resistance in the radial clearance 4 and the axial clearance 5 to become atmospheric pressure and is discharged outside the bearing. . However, the flow path resistance in the carbonaceous porous body 2 does not change, but the flow path resistance in the radial clearance 4 and the axial clearance 5 significantly changes depending on the size of the clearance (inversely proportional to the cube of the clearance). Therefore, if the hydrostatic bearing receives some external force and, for example, a difference occurs between the opposing radial clearances 4 or the axial clearances 5, the flow path resistance on the side where the clearance is reduced increases, and the pressure in the clearance rises accordingly. . However, since the gap on the opposite side is just the opposite, the pressure in the gap drops. As a result, the hydrostatic bearing acts so as to increase or decrease the pressure in the opposing gaps so that the flow resistances in the opposing radial gaps 4 and the opposing axial gaps 5 are always constant. Usually, a value obtained by dividing a value obtained by converting the pressure change into a force by the amount of change in the gap is called a spring constant, that is, rigidity. The higher the rigidity and the higher the rotation accuracy, the higher the performance of the hydrostatic bearing. In addition, in the porous hydrostatic bearing, the flow path resistance of the porous body is designed to be approximately 1/2 to 3/4 of the bearing gap. Therefore, if the bearing gap can be designed to be small, the flow path resistance as a whole becomes large, so that the static pressure bearing has a low flow rate and high rigidity. On the other hand, most of the flow passage resistance in the bearing gap is the frictional resistance between the fluid and the wall surface of the gap, but the flow passage resistance of the porous body is such that if the thickness of the fluid passage in the porous body is thinner than the bearing gap, The friction resistance with the wall surface (capillary squeeze) is the main, but it is not easy to manufacture a porous body having a fluid passage finer than the bearing gap. Even if it can be manufactured, control of the flow path resistance between the fluid inlet and outlet is a problem, as will be described later.

It is the clearance between the bearings that most affects the high rigidity of the hydrostatic bearing. This is because the smaller the gap, the more the pressure rises and falls in response to minute changes in the gap, resulting in higher rigidity (inversely proportional to the gap) and a drastic reduction in the amount of fluid supplied to the bearing gap ( It can be inversely proportional to the cube. Further, since the member precision is increased because the gap between the shaft and the bearing is reduced, the rotation precision is also improved accordingly. In this way, miniaturization of the bearing gap is directly related to higher performance of the hydrostatic bearing by higher precision itself. However, the improvement in accuracy depends largely on the characteristics of the material to be processed, such as strength, hardness, expansion coefficient, and dimensional stability. Since the carbonaceous porous body 2 which is inferior in strength and hardness to the ceramic material which can be processed with high precision is not suitable for precision processing, it has a drawback that further static rigidity of the hydrostatic bearing is restricted. . Further, since the carbonaceous porous body 2 has low strength, if the air supply pressure is high, it will be deformed or broken in the axial direction or the radial direction due to the internal pressure of the air supply groove 8. For this reason, the carbonaceous porous body 2 has a drawback that its size is larger than that of metal or ceramic in terms of strength. Particularly, the disadvantage of the strength of the carbonaceous porous body 2 is limited to the application to the static pressure gas bearing (about 0.5 MPa), which may have a low supply pressure,
This makes it difficult to apply to hydrostatic liquid bearings (about 5 MPa or more). In addition, it goes without saying that even if high precision is realized, the performance of the hydrostatic bearing will be adversely affected unless the air is properly supplied to the bearing gap. The design values of the radial clearance 4 and the axial clearance 5 are generally determined from the workable accuracy. In addition, the flow rate of air supply is determined by back-calculating the flow path resistance from this design value. However, in order to pass through the inside of the carbonaceous porous body 2 through only one air supply hole 7 to supply the flow rate determined by the radial gap 4 and the axial gap 5 at different places, the shape and permeability of the carbonaceous porous body 2, Since the layout of the air supply groove 8 is complicatedly related, its design is not easy. Even if it can be designed, the quality of the carbonaceous porous body 2 manufactured by the sintering method is likely to change depending on the conditions such as the particle size of the carbon powder, the binder, the pressure and temperature at the time of molding, and the homogeneity and the desired transmittance. Carbonaceous porous body 2
It's not easy to get. As described above, the carbonaceous porous body has various drawbacks in terms of member strength, suitability for high-precision machining, ease of designing and manufacturing, and the like in further improving the performance of the hydrostatic bearing.

On the other hand, if only the carbonaceous porous body 2 shown in FIG. 5 is replaced with a ceramic porous body, a hydrostatic bearing can be realized which solves the drawbacks of the carbonaceous porous body such as low member strength and lack of suitability for high precision machining. . However, this does not mean that design / manufacturing is easy. The biggest drawback of the conventional hydrostatic bearing using such a porous body is that it cannot be designed and manufactured easily. The cause is that the porous body has different roles of fluid passage and throttle. is there. That is, in the hydrostatic bearing having the conventional structure, the flow path resistance from the air supply hole 7 to the axial gap 5 and the radial gap 4, that is, the amount of fluid throttling is not determined only by the permeability of the porous body, and the structure and shape of the porous body are determined. The close relationship is a cause of hindering the ease of design and manufacturing. On the other hand, the porous body also serves as a passage for the fluid and a throttle, but the flow resistance of the porous body is
There is a method in which the channel resistance is manufactured to be slightly smaller than the actually required channel resistance, and the channel resistance after manufacturing the bearing is accurately controlled to the actually required transmittance. After manufacturing a bearing member corresponding to the carbonaceous porous body 2 of FIG. 5 using a porous body having a transmittance slightly smaller than the required transmittance as this example, the axial clearance 5 and the radial clearance 4 are formed. A method shown in FIG. 6 in which the cross-sectional area of the fluid passage in the porous body is reduced by applying electroless nickel plating (hereinafter referred to as “plating”) to the surface of the porous body to control the transmittance, that is, the throttle amount of the fluid ( (Japanese Patent Laid-Open No. 64-6515)
There is.

FIG. 6 is a schematic view showing a cross section of a porous body whose transmittance is adjusted by plating. 10 is a meat part of the porous body, 11 is a hole existing between the meat parts 10, and 12 is meat quality. The plating film adhered to the surface of the portion 10, 13 is a bearing surface, 14
Is the bearing gap. Usually, in a porous body produced by sintering or the like, the constituent molecules and the sintering aid are thermally diffused and bonded between the sintered particles at a temperature equal to or lower than the melting point. Therefore, the pores formed between the particles have a three-dimensional structure in which the pores 11 are connected in a dumpling shape as shown in the figure. Therefore, the fluid passing therethrough has a transmittance, that is, a flow path resistance, determined by the influence of the cross-sectional area between the holes 11 having the smallest cross-sectional area. The transmittance adjustment by plating is controlled by reducing the cross-sectional area between the holes 11 by the thickness of the plating film 12.
However, according to this method, since the cross-sectional area between the pores 11 is originally large or small, if the thickness of the plating film 12 is increased, the plating film 12 seals from the cross-sectional area between the small pores 11 first, so that the bearing surface The fluid outlet on 13 is gradually reduced. Conversely, it means that the cross-sectional area between the small holes 11 is sealed and controlled. As a result, a large cross-sectional area between the holes 11 remains roughly, which makes it difficult to uniformly supply the fluid to the bearing gap 13. Further, the holes 11 originally opened on the bearing surface 13 are left behind even after plating and become a bearing useless gap to reduce the rigidity of the hydrostatic bearing, or a pneumatic hammer peculiar to an aerostatic bearing, that is, an air bearing. It causes self-excited vibration due to the compressibility of. There are drawbacks, etc.

In addition, the bearing clearance of the porous bearing is usually 5 μm.
The following is normal: In this case, if the flow path resistance of the porous body is mainly frictional resistance (capillary diaphragm) with the wall surface of the porous body as described above, the diameter of the pores 11 is also 5 μm or less,
In particular, the reduced area of the cross-sectional area due to plating must be of the order of μm. Further, if the diameter of the pores 11 is 5 μm or less, even if gas can enter the porous body, in addition to the penetration of the plating solution, which is a liquid, there are difficulties in controlling the transmittance itself by plating. For this reason, since a porous body having pores 11 that is significantly larger than the bearing gap is used, the transmittance control is unavoidable in which residual pores 11 on the bearing surface and uneven fluid supply cannot be avoided. Therefore, in practice, the flow resistance of the porous body controlled by plating is such that the ratio of the frictional resistance with the wall surface of the porous body (capillary squeezing) is reduced, and the flow resistance from the small holes on the surface of the porous body (orifice squeezing) and bearing clearance It becomes a diaphragm in which a step formed by the shape of the porous body surface and an outflow resistance (a surface diaphragm, a self-made diaphragm) due to a void are mixed. Since these throttles have different characteristics as throttles, there is a variation in the performance of the hydrostatic bearing due to the mixing ratio. Capillary throttles and orifice throttles show a constant flow resistance regardless of changes in bearing clearance, but face diaphragms and self-made throttles decrease flow resistance when the bearing clearance increases and decrease when the clearance decreases. It shows a rising characteristic. As for the effect of increasing the rigidity of the bearing, the better the mixing ratio of the capillary throttle or the orifice throttle, the better the effect. It should be noted that the best characteristic is that the flow path resistance increases as the bearing clearance increases, and the flow resistance decreases as the clearance decreases, but there is no such throttle at this time. As described above, there are various drawbacks in the structure of the hydrostatic bearing that uses the transmittance control by plating.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been proposed to remedy the above-mentioned drawbacks, and its object is to provide a porous means provided with a new fluid passage forming means and a fluid throttle control means. It is to provide a hydrostatic bearing and a manufacturing method thereof.

[0009]

In order to achieve the above-mentioned object, the present invention is a hydrostatic bearing for supplying a fluid to a gap between solids to float in a non-contact manner, which is connected to a fluid supply hole, and A porous body having an opening in a part of the bearing gap is enclosed inside the dense ceramic, and the opening of the bearing gap of the porous body is porous in a porous body formed by embedding and fixing small diameter particles with a binder. A characteristic feature of the present invention is a porous ceramic hydrostatic bearing. further,
The present invention relates to a method for producing a ceramic porous hydrostatic bearing in which a porous body which is connected to a fluid supply hole and has an opening in a part of a bearing gap is enclosed inside a dense ceramic, wherein SUMMARY OF THE INVENTION A method of manufacturing a ceramic porous hydrostatic bearing, characterized in that a porous body is integrally formed by a slurry casting method, and small-diameter particles are embedded and fixed in an opening of the bearing gap of the porous body by a binder. It is what In other words, according to the first aspect of the present invention, that is, as a structure of the fluid passage, a porous body that is connected to the fluid supply hole inside the dense ceramic and has an opening in a part of the bearing gap is included. The partial porous body from the bearing gap to the bearing gap is limited to the fluid passage to form a static pressure bearing component having no throttle control function. As a second means, that is, fluid throttling control, particles smaller than the cross-sectional area of the opening are embedded and fixed in the opening of the porous body having an opening in a part of the bearing gap to form a porous body in the porous body. The cross-sectional area of the partial porous body opening is reduced to control the flow path resistance, that is, the fluid restriction. The above two means limit the porous body only to the role of the passage of the fluid, and the control of the fluid restriction is separately controlled by the embedding and fixing method of the particles. Therefore, not only the strength and accuracy of the hydrostatic bearing member made of porous ceramic are improved, but also the formation of the fluid passage and the control of the throttle are separated and independent.

[0010]

In the present invention, the throttle control of the fluid passage is formed by embedding and fixing small-diameter particles in the opening forming the bearing surface, so that the throttle control can be performed with high precision.

[0011]

EXAMPLES Next, examples of the present invention will be described. Figure 1
FIG. 1 is a sectional view of an embodiment showing the structure of a hydrostatic bearing of the present invention, in which reference numeral 15 denotes a ceramic partial porous body made of ceramic in which a partial porous body is integrally formed inside a hollow cylinder. is there. Reference numeral 16 is a part of the ceramic partial porous body 15 and is a porous body integrally formed in the ceramic partial porous body 15 to serve as a fluid passage, and 17 is an axial gap outlet of the same material as the porous body 16. An annular opening is formed on the axial end surface of the ceramic partial porous body 15. Reference numeral 18 denotes a radial clearance outlet of the same material of the porous body 16, which is also opened annularly toward the inside of the hollow cylinder of the ceramic partial porous body 15. 7 is a partially porous ceramic body 15
Is an air supply hole formed in the porous body 16 from the outside. However, at this stage, the porous body 16 has a permeability that greatly exceeds the fluid supply amount required for the axial gap 5 and the radial gap 4. The opening of the bearing gap of the porous body is formed by embedding and fixing small diameter particles with a binder. With such a structure, when the pressurized fluid is supplied to the air supply hole 7, the fluid is diverted from the porous body 16 to the axial gap outlet 17 and the radial gap outlet 18, and the axial gap 5 and the radial gap 4 are respectively separated. It passes through and is released outside the bearing at atmospheric pressure. The function of the hydrostatic bearing is the same as that of the conventional carbonaceous porous body 2, and the description thereof is omitted.

Next, an example of a method for manufacturing the ceramic partial porous body 15 will be briefly described. In order to form a porous part having a specific shape inside the ceramic, a shape forming method called a slurry casting method is used. The normal slurry casting method is
When a slurry (hereinafter referred to as a slurry) in which ceramic particles and a sintering aid are dispersed in water is poured into a gypsum mold having the required outer frame shape, the water in the slurry is gradually absorbed by the gypsum mold. Ceramic particles settle on the mold. As a result, a cast product of ceramic particles equivalent to a gypsum mold is completed. The slurry casting method is to dry and sinter this into a ceramic. Although the ceramic produced by the slurry casting method is dense and has high strength, it is impossible to make a specific portion of the ceramic into a porous body by simply casting the slurry. To make a specific part of the ceramic porous, the shape of the specific part is the same, for example, urethane foam or PVF used in the bathroom.
A sponge made of (polyvinyl acetal) is set in a plaster mold in advance and the slurry is poured into it to produce a cast product containing the sponge. When this is sintered, the sponge sublimes during sintering, so it is a conventional sponge. As a result of forming the voids in the exposed portions, it is possible to manufacture a porous ceramic only in the specific portions.

Since the cast product before sintering, which is produced by sludge casting, generally shows the properties of a black ink used when writing letters and pictures on a blackboard, it can be easily cut into a desired shape by cutting or the like. Can be processed. However, since it shrinks due to sintering, it is necessary to make it larger by that amount. However, after sintering, it changes into a dense and high hardness ceramic, so only grinding or polishing can be applied, but extremely high finishing accuracy can be obtained. In addition, when a partially porous ceramic is manufactured by the slurry casting method, if the ceramic particles are not filled in all of the pores of the sponge, a nest will form inside,
Sponge with coarse pore density is more suitable for sludge casting. Therefore, it is more advantageous for forming a porous body having a higher permeability, that is, a coarser porous body than for forming a porous body having a lower permeability, that is, a dense porous body. As described above, the slurry casting has a problem in manufacturing a dense porous body having a small transmittance, but has an advantage that accuracy can be improved. However, as mentioned above, the increase in rigidity of the hydrostatic bearing is closely related to the minimization of the bearing gap, and the higher the precision, the greater the flow resistance of the bearing gap. Also needs to be increased in proportion to this. However, although a ceramic porous body obtained by sludge casting is suitable for high precision, it is not suitable for obtaining a porous body having a high density and a large flow resistance. However, since the flow path resistance is low, it is suitable as a fluid passage. The above has described the structure of the hydrostatic bearing according to the present invention, in particular, the structure of the fluid passage made of ceramics and an example of the manufacturing method thereof. Hereinafter, a new method of controlling the aperture will be described.

FIG. 2 shows the throttle control method of the present invention applied to the fluid outlet of the partially porous ceramic material 15 manufactured by sludge casting shown in FIG. 1, that is, the axial gap outlet 17 or the radial gap outlet 18. It is a schematic diagram of an expanded cross section. However, the structure of the porous body is the same as that in FIG. 1 for easy understanding. Reference numeral 19 is a small-diameter particle for permeability control, which is embedded and fixed in the hole 11 existing in the opening of the fluid passage of the partially porous ceramic body 15. By embedding and fixing the small-diameter particles 19 in the fluid outlet of the partially porous ceramic body 15, the cross-sectional area of the fluid passage is reduced to control the passage rate, that is, the flow path resistance. The embedding of the small diameter particles 19 is carried out by filling the small diameter particles 19 in the ceramic partial porous body 15 and fixing the small diameter particles 19. Hereinafter, the embedding and fixing of the small diameter particles 19 will be described.

FIG. 3 is a schematic view showing an example of an instrument structure for embedding and fixing the small-diameter particles 19. Reference numeral 17 denotes an axial gap outlet of fluid on the partially porous ceramic body 15, and 18
Is a radial gap outlet, 20 is a circular ring seal for individually masking the axial gap outlet 17, 21 is a cylindrical seal for individually masking the radial gap outlet 18, and 22 is a small particle 1
A slurry in which 9 is dispersed in a tetraethoxysilane binder, 23 is a dropper for collecting the slurry 22,
24 is a spatula for removing the excess slurry 22.
25 is a vacuum pump for evacuating the inside of the ceramic partial porous body 15, and 26 is the ceramic partial porous body 1.
5, a separator for removing the small-diameter particles 19 and Ban-Ida liquid that have passed through the inside 5, a vacuum gauge 27 for observing the pressure inside the separator 26, a filter 28 for passing a gas other than gas into the vacuum pump 25, Reference numeral 29 is a vacuum hose that connects among the ceramic partial porous body 15, the separator 26, the filter 28, and the vacuum pump 25. The procedure for embedding the small-diameter particles 19 will be described below.

After masking parts other than the axial gap outlet 17 for filling the small particle 19 with the circular ring seal 20 and the cylindrical seal 21, the inside of the ceramic partial porous body 15 is exhausted by operating the vacuum pump 25. Next, when the slurry 22 in the dropper 23 is supplied to, for example, the axial gap outlet 17, the slurry 22 is vacuum-sucked into the porous body, and as shown in FIG. The small-diameter particles 19 fill the inside of the passage of the porous body by staying in the cross-sectional area between the pores 11 having the smallest cross-sectional area, which triggers. However, since the binder in the slurry 22 is a viscous liquid, most of it is removed through the gaps between the small-diameter particles 19, but the binder adhered to the small-diameter particles 19 and the wall surfaces of the pores 11 is left behind. Since this binder is cured after a certain period of time, a large number of small particles 19 can be embedded and fixed in the pores 11. After the curing, the binder strength of the binder can be significantly increased by firing in a furnace.

FIG. 4 is a schematic enlarged view of the state in which the small-diameter particles 19 are embedded and fixed, as viewed from the bearing surface 13 side in FIG. 1
Reference numeral 0 represents the meat portion of the ceramic partial porous body 15, 30 represents a new passage for a fluid newly opened between the embedded and fixed small diameter particles 19, and 31 is left behind between the wall surface of the meat portion 10 and the small diameter particles 19 and hardened. It is a binder. As shown in the drawing, the pores 11 that existed between the fleshy portions 10 in the related art are filled with small-diameter particles 19 to form a porous body in the porous body, which makes it difficult to distinguish, but the pores 11 have new passages 30 of various sizes. A large number can be formed three-dimensionally, and the cross-sectional area of the fluid passage can be greatly reduced. Although the schematic diagram is illustrated with the small-diameter particles 19 having the same diameter and the binder 31 having the same thickness for easy understanding, the size of the pores 11 of the ceramic partial porous body 15 to be controlled in the actual embedding fixation. However, the diameter of the small particles 19 and the viscosity of the binder 31 can be selected, and the slurry 22 having different diameters can be used multiple times, or the exhaust pressure can be controlled by the vacuum pump 25 or the like for throttle control. There are many conditions. Therefore, it is not difficult to select the conditions for setting the transmittances of the axial clearance outlet 17 and the radial clearance outlet 18 shown in FIG.

The tetraethoxysilane binder will be briefly described below. The basic chemical structure of tetraethoxysilane is

[Chemical 1] It reacts with water in the presence of a catalyst to produce silica (SiO ₂ ) as follows. Si (OC ₂ H ₅ ) ₄ + 2H ₂ O → (catalyst) → SiO ₂
+ 4C ₂ H ₅ OH This contains about 28% silica and tetraethoxysilane, ethanol and the like. Further, what is concentrated to a silica content of about 40% by partial hydrolysis is generally used as a silica raw material. For the bainida, a hydrolyzed solution obtained by mixing a solvent, water, an acidic catalyst and the like is used. It is considered that SiO ₂ is colloidally dispersed in an alcohol solvent in a normal hydrolysis solution, and when particles are mixed with this hydrolysis solution and applied, the SiO ₂ film is formed by wrapping the particles or filling the gaps. To be done. By this action, the particles are fixed to the surface of the object, or the particles are solidified and shaped. Typical applications include sand wax type solid agents used for precision casting such as lost wax and show process, and surface hardening agents for plastic materials. It should be noted that the hydrolyzed liquid contains extremely fine S
The viscosity can be adjusted by mixing the iO ₂ fine particles. Further, when SiO ₂ is used, it has excellent chemical resistance when cleaning the fluid passage, has hydrophilicity, and therefore can be easily plated, and since it has moisture resistance, the change in resistance due to swelling is small.
Since it is strong against heat, it is easy to strengthen the adhesion force by reheating after determining the resistance. Furthermore, since SiO ₂ has a solvent (hydrofluoric acid), it can be removed without damaging the ceramics, and the resistance can be readjusted and the base ceramics can be recycled. The two means for controlling the structure of the fluid passage and the control of the fluid throttle for improving the drawbacks of the conventional hydrostatic bearing have been described above.

However, it goes without saying that in the first means of the embodiment, it is possible to manufacture a ceramic in which only a specific portion is made porous by an ordinary sintering method in which ceramic particles are sintered and bonded. The point is that the porous body has a transmittance that does not act as a restriction of the fluid as in the conventional case. As described above, in order to cause the porous body to act as a restriction of the fluid, as shown in FIG.
The average diameter of the holes shown in Fig. 3 is less than the clearance of the bearing, and the flow resistance of the porous body is 1/2 to 3/4 of the flow resistance of the bearing clearance.
Is desirable. However, if the fluid passage structure and throttle control of the present invention are used, even if the average diameter of the holes is larger than the bearing gap by one digit or more, the flow passage resistance of the porous body is 1 / one of the flow passage resistance of the bearing gap.
Needless to say, even if it is 10 or less, ease of manufacture is prioritized. Incidentally, the permeability K of the porous body suitable for the constitution of the fluid passage of the present invention is expressed by K = (Q · L) / (ΔP · A) (cm ³ / sec) · c
m / cm ² · cmH ₂ O gas flow rate Q (cm ³ / sec), permeation thickness L (cm),
When defined as pressure difference ΔP (cmH ₂ O) and permeation cross-sectional area A (cm ² ), the value of K is around 1 × 10 ^-2 , and the average diameter of pores is about 50 μm to 150 μm by sludge casting. It is easy to manufacture and is suitable for diaphragm control. Alumina (AL ₂ O ₃ ) is usually used as the ceramic material, but the material is not limited to this. For example, silicon nitride (Si 2
It goes without saying that N) or silicon carbide (SiC) may be used.

Although the material of the small-diameter particles is not specified in the second means of the embodiment, silicon oxide (SiO ₂ ) having the same material as the tetraethoxysilane-based binder is suitable, but the material is not limited to this. Needless to say, a powder made of ceramic or metal, or originally small particles having a small diameter may be used. It goes without saying that the size of the small-sized particles also needs to be selected according to the design of the target porous or hydrostatic bearing. Further, the small-diameter particles were embedded and fixed with a tetraethoxysilane-based binder, but the present invention is not limited to this, and it is needless to say that the transmittance may be adjusted by conventional electroless plating after the temporary fixing. Is characterized in that it is embedded and fixed in a porous body with a binder to form a porous body in the porous body. The new constituent means of the fluid passage made of the ceramic porous body and the new diaphragm forming means made of the porous body in the porous body have been described in detail with reference to the embodiments. In the configuration of the fluid passage in the conventional porous hydrostatic bearing, the passage itself of the porous body is configured to serve as a means for controlling the flow resistance, whereas the configuration of the fluid passage of the present invention is the opposite of the conventional configuration. It is configured so as not to serve as a flow path resistance control means. The construction method is completely opposite to the conventional one and there is a big difference. Further, while the flow path resistance control means in the conventional porous static pressure bearing controls the flow path resistance of the porous flow path constituting the fluid passage, the flow path resistance control means of the present invention comprises a porous body forming the fluid passage. Controls the flow path resistance of porous media with completely different densities and manufacturing methods. That is, there is a big difference in that the porosities to be controlled are completely different.

[0021]

As described above, since the structure of the fluid passage in the hydrostatic bearing of the present invention is made of ceramic and the porous body can be limited to the role of the fluid passage, the following effects can be obtained. (1) The porous body only needs to be a fluid passage having a sufficiently high permeability, and since a precision is not required so much in the constituent dimensions and the permeability of the porous body, its homogeneity and variations, etc., there is a margin in design and manufacturing. (2) The porous body is the minimum necessary fluid passage, and most of the bearing structure can be made of dense ceramic having high strength and hardness. Therefore, not only the static pressure bearing can be downsized by this amount, but also the supply pressure can be increased, so that it can be applied to the static pressure liquid bearing. (3) It can be made of ceramic suitable for high-precision machining. Therefore, it is possible to achieve high rigidity, low air supply flow rate, high rotation accuracy, and the like, which are closely related to high accuracy of the hydrostatic bearing. Further, the throttling control of the fluid passage according to the present invention has the following effects because small-sized particles are embedded and fixed in the openings of the porous body forming the bearing surface to form the porous body in the porous body. (4) Aperture control can be performed with high accuracy by the amount that can be controlled while observing the transmittance, that is, the flow path resistance. (5) Since the density of the porous material in the porous body can be changed by selecting the size of the small diameter particles, the viscosity of the binder, etc., the control range of the fluid restriction can be greatly expanded. (6) In the porous body of the porous body, a large number of small fluid outlets can be formed due to the miniaturization of the porous density, and the distribution of the fluid supply to the bearing gap can be made uniform. (7) Since a large number of small fluid outlets, that is, orifice orifices, which have superior throttle characteristics, can be formed on the bearing surface, high rigidity of the hydrostatic bearing can be achieved. (8) Since the pores of the porous body opening on the bearing surface are filled with the small-diameter particles and the binder, the waste clearance can be reduced by that much, and the rigidity of the bearing can be increased and the pneumatic hammer can be reduced. In addition to overcoming the design and manufacturing deficiencies of conventional porous hydrostatic bearings, there are many advantages that can significantly improve the application range and overall performance of porous hydrostatic bearings. It will be possible to realize a hydrostatic bearing with low flow rate, high rigidity, high speed and high accuracy, which takes advantage of the advantages.

Although the invention has been described in detail above by taking the static pressure lubrication between the shaft and the bearing as an example, if the shaft and the bearing are replaced by guides and sliders, or screw shafts and nuts, the shaft and the bearing can rotate. Guides, guides and sliders are linear guides, and screw shafts and nuts are spiral guides. Therefore, it is needless to say that the basic idea of the method of constructing the fluid passage and the throttle in the porous hydrostatic bearing of the present invention can be applied to all hydrostatic lubrication mechanisms. Furthermore, the hydrostatic bearing of the present invention can be applied to non-contact fluid lubrication using not only gas but also liquid, and the performance thereof can be remarkably improved as compared with the conventional one. Therefore, when the present invention is applied to a spindle, a guide, a stage, a hydrostatic screw, or the like as a mechanical component using the hydrostatic lubrication, the feature can be fully utilized.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment showing the structure of a hydrostatic bearing of the present invention.

FIG. 2 is a schematic view of an enlarged cross section subjected to the aperture control method of the present invention.

FIG. 3 is a front view of a schematic view showing an example of a device configuration for embedding and fixing small-diameter particles.

FIG. 4 is a cross-sectional view of a schematic enlarged view showing a condition of a bearing surface in which small-diameter particles are embedded and fixed.

FIG. 5 is a sectional view showing an example of a conventional hydrostatic bearing using a carbonaceous porous body.

FIG. 6 is a schematic view of a cross section of a porous body having a plating transmittance adjusted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 rotating shaft 2 carbonaceous porous body 3 face plate 4 diameter clearance 5 axial clearance 6 case 7 air supply hole 8 air supply groove 9 exhaust port 10 fleshy portion 11 void 12 plating film 13 bearing surface 14 bearing clearance 15 ceramic partial porous body 16 Porous body 17 Axial clearance outlet 18 Diameter clearance outlet 19 Small particle 20 Circle ring seal 21 Cylindrical seal 22 Slurry 23 Dropper 24 Spatula 25 Vacuum pump 26 Separator 27 Vacuum gauge 28 Filter 29 Vacuum hose

Claims (2)

[Claims] 1. In a hydrostatic bearing for supplying a fluid to a gap between solids to float without contact, a porous body connected to a fluid supply hole and having an opening in a part of the bearing gap is a dense ceramic. A ceramic porous hydrostatic bearing characterized in that the opening of the bearing gap of the porous body is a porous body in a porous body formed by embedding and fixing small diameter particles with a binder. 2. A method for producing a ceramic porous hydrostatic bearing in which a porous body which is connected to a fluid supply hole and has an opening in a part of a bearing gap is enclosed inside a dense ceramic. And the porous body are integrally formed by a slurry casting method, and small-diameter particles are embedded and fixed in an opening of the bearing gap of the porous body by a binder, and a method for manufacturing a ceramic porous hydrostatic bearing.