JP4465840B2 - Method for producing porous hydrostatic gas bearing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a porous static pressure gas bearing using a porous metal sintered body.
[0002]
[Problems to be solved by the invention]
Porous hydrostatic gas bearings have been attracting attention as having excellent high-speed stability and high load capacity, and various studies have been made, but there are some problems to be overcome in practical use.
[0003]
Bronze sintered bodies, porous carbon, ceramics, etc. are known as porous bodies used for porous hydrostatic gas bearings, but the surface of porous hydrostatic gas bearings has a surface of the order of 1 μm. Since roughness is required, in many cases, machining such as grinding is performed on the surface of the porous body serving as the bearing surface.
[0004]
In a bronze sintered body, if grinding is performed to obtain a bearing surface, plastic flow of bronze is induced on the ground surface (bearing surface), and burrs and burrs are generated in the pore openings. Wrapping is performed to obtain proper air permeability.
[0005]
Porous carbon and ceramics have high brittleness, so there are almost no burrs or burrs in the opening of the pores due to the grinding process, so clogging due to this hardly occurs, but the pores on the bearing surface If there are many such openings, they will cause self-excited vibration (pneumatic hammer phenomenon), and the gas consumption will become large and uneconomical. Then, an adhesive is applied to the bearing surface to appropriately clog the opening of the pores, thereby preventing self-excited vibration and proper air permeability.
[0006]
By the way, since the bearing surface is required to have extremely high shape accuracy, there is a certain limitation in removing burrs and burrs by lapping in order to maintain the shape within the accuracy after grinding. Therefore, there is a limit to obtaining an appropriate flow rate by lapping, and even if an adhesive is applied to the bearing surface after grinding, it is extremely difficult to control the coating amount, and the bearing surface is highly accurate. In order to maintain the shape dimension and the surface roughness, an extremely complicated and precise operation for removing the remaining adhesive from the bearing surface after application is required.
[0007]
Furthermore, in any case of sintered bronze, porous carbon, and ceramics, there is a risk that chips and abrasive grains will be buried and remain in the pores after grinding. If it is removed from the pores during use and jumps to the outside, the air permeability may be changed and the usage environment will be contaminated. Therefore, the bearing is not suitable for use in the ultra-precision field. .
[0008]
The present invention has been made in view of the above-mentioned points, and its object is to easily obtain appropriate and stable air permeability, and at the same time, chips and abrasives buried in the pores. An object of the present invention is to provide a method for producing a porous hydrostatic gas bearing capable of removing particles.
[0009]
[Means for Solving the Problems]
The method for producing a porous hydrostatic gas bearing in which the air permeability of the porous metal sintered body of the first aspect of the present invention is adjusted is obtained by mixing and sintering a metal powder and an inorganic powder. A step of preparing a metal sintered body, a step of grinding one surface of the porous metal sintered body to form a bearing surface, and a liquid that is ultrasonically vibrated in the porous metal sintered body on which the bearing surface is formed. A step of increasing the opening area of the pores of the bearing surface of the porous metal sintered body by being immersed therein.
[0010]
According to the method of the first aspect, in order to use a porous metal sintered body obtained by mixing and sintering a metal powder and an inorganic powder, the metal portion of the porous metal sintered body is plastically flowed by grinding. Then, a part of the inorganic part ground brittlely and the pores between the inorganic part and the metal part are covered, and chips and abrasive grains are buried in the pores. As a result of immersing a porous metal sintered body composed of a part and an inorganic part in a liquid that is ultrasonically vibrated, first, the chips and abrasive grains buried in the pores can be removed, and based on the chips and abrasive grains Clogging can be eliminated, uncertain air permeability due to chips and abrasive grains can be eliminated, and since chips and abrasive grains are not scattered during the use environment, a clean environment can be maintained. The plastic flow part of the metal part and the weak part of the inorganic part can be crushed to increase the pore opening area. The air permeability of the porous metal sintered body can be adjusted without obstructing the shape accuracy and surface roughness of the bearing surface after grinding, and thus appropriate and stable air permeability can be easily obtained. .
[0011]
The metal powder for forming the porous metal sintered body usually has a particle size of 30 μm to 150 μm, preferably 45 μm to 75 μm. Similarly, the inorganic powder has a particle size of usually 30 μm to 300 μm. Preferably, those having a thickness of 45 μm to 150 μm are used. The sintered density and porosity of the porous metal sintered body using such metal powder and inorganic powder differ depending on the sintering time and the sintering temperature. For example, a pressure of ^{2 to} 7 tons / cm ² is applied. When a green compact is formed and the green compact is sintered in a reducing atmosphere or vacuum at a temperature of 800 to 1150 degrees for 20 to 60 minutes, the sintered density is generally 5.15 g / cm ^{2 to} 6.19 g / cm ² and the porosity is 21.1% to 34.1% (in terms of oil content).
[0012]
In the present invention, desired air permeability can be obtained by appropriately adjusting the immersion time of the porous metal sintered body in the liquid that is ultrasonically vibrated as described above.
[0013]
The liquid for immersing the porous metal sintered body is preferably one that can remove the oil content of the grinding fluid. However, from the viewpoint of simplicity, low cost, environmental pollution, etc., the method of the second aspect of the present invention. Thus, it is preferable to use water, ethanol or an alkaline solution.
[0014]
The frequency of the ultrasonic vibration applied to the liquid may be appropriately determined in relation to the air permeability required for the porous metal sintered body, but usually a frequency of about 40 to 100 KHz is preferably used.
[0015]
By the way, in the case of excessive air permeability after ultrasonic vibration, as in the method of the third aspect of the present invention, the fineness of the porous metal sintered body after being immersed in a liquid that is ultrasonically vibrated. After injecting a liquid in which a predetermined amount of resin is dissolved in a solvent such as toluene into the pores, air may be injected into the pores, and such liquid is injected into the pores and air is injected. By attaching a resin having an appropriate thickness to the pores, the diameter of the pores can be reduced, and the air permeability can be set to a desired value.
[0016]
As the resin dissolved in the solvent, a silicone resin is preferably used as in the method of the fourth aspect of the present invention, but other resins such as a phenol resin may be used. In addition, by using liquids having various resin concentrations, the thickness of the resin attached to the pores can be changed, and thereby desired air permeability can be obtained. Further, according to this method, the scattering of foreign matters into the use environment can be prevented more reliably, and it is effective for maintaining a clean environment.
[0017]
In the method of the fifth aspect of the present invention, the metal powder that is the material of the metal part in the porous metal sintered body contains at least tin, phosphorus, and copper, and the inorganic powder that is the material of the inorganic part is: In the method of the sixth aspect of the present invention, the metal powder further comprises at least one of graphite, boron nitride, graphite fluoride, calcium fluoride, aluminum oxide, silicon oxide, and silicon carbide. Contains nickel or manganese.
[0018]
The porous hydrostatic gas bearing manufactured according to the present invention may be either a cylindrical or plate-like thrust bearing or a radial bearing, and may be a linear motion bearing, a so-called slider.
[0019]
Hereinafter, the present invention and embodiments of the present invention will be described based on preferred examples with reference to the drawings. The present invention is not limited to these examples.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
In the method of the present invention, first, a cylindrical porous metal sintered body 1 as shown in FIG. 1 is prepared by mixing and sintering a metal powder and an inorganic powder. The porous metal sintered body 1 is, for example, a mixed powder composed of 4 to 10% of tin, 10 to 40% of nickel, 0.5 to 4% of phosphorus, 3 to 10% of graphite, and the remaining copper in a weight ratio of 2 tons, for example. A cylindrical green compact is produced by pressure forming at 7 ton / cm ² , and the green compact is sintered in a reducing atmosphere or vacuum at a temperature of 800 to 1150 degrees for 20 to 60 minutes. Form.
[0021]
The porous metal sintered body 1 thus formed is inserted into a cylindrical housing (casing) 30 as shown in FIG. The housing 30 of this example has an annular recess 31 on the inner peripheral surface and a passage 32 communicating with the recess 31, but the housing is not limited to such a housing 30.
[0022]
In the porous metal sintered body 1 inserted into the housing 30, the cylindrical inner peripheral surface 2 is ground and then ground to form the inner peripheral surface 2 as a bearing surface, and the circle. Sealing treatment is performed on the annular end faces 34 and 35 using an appropriate sealing agent. The machining allowance in grinding is preferably performed in a range of approximately 0.2 mm or less.
[0023]
As shown in FIGS. 3 and 4, the ground inner peripheral surface 2 includes an opening 12 of the pore 11 and an exposed surface 14 of the metal portion 13 made of metal powder made of tin, phosphorus, nickel, and copper. And the exposed surface 16 of the inorganic portion 15 made of an inorganic powder are randomly distributed, and the exposed surface 14 of the metal portion 13 is spread by the plastic flow of the metal portion 13 by grinding. Including the exposed surface 18 of the part 17, such an extended part 17 being the opening 12 of the pores 11, part of the brittlely ground inorganic part 15 and between the inorganic part 15 and the metal part 13. Covering the opening 12 of the pore 11, the pore 11 is squeezed by the opening 12, and part of the inorganic portion 15 also squeezes the pore 11 by the opening 12.
[0024]
The porous metal sintered body 1 in which the inner peripheral surface 2 as such a bearing surface is formed and fitted in the housing 30 is then used as the ultrasonically vibrated liquid in the container 21 as shown in FIG. Immerse in 22 As the liquid 22, water, ethanol, or an alkaline liquid is used. The immersion time is determined in relation to the frequency of ultrasonic vibration used and the required air permeability.
[0025]
By immersing in the ultrasonically vibrated liquid 22, the opening area of the pores 11 on the inner peripheral surface (bearing surface) 2 of the porous metal sintered body 1 is increased, and the air permeability of the porous metal sintered body 1 is increased. After the adjustment, the porous metal sintered body 1 is taken out from the container 21 and dried at room temperature to obtain a porous hydrostatic gas bearing made of the cylindrical porous metal sintered body 1.
[0026]
FIG. 6 shows an example in which the relationship between the immersion time in the liquid 22 that is ultrasonically vibrated and the air permeability is obtained for the frequencies of ultrasonic vibration of 45 kHz and 100 kHz. As the porous metal sintered body 1, one having an inner diameter of 25 mm, an outer diameter of 35 mm, and a length of 25 mm was used, and the liquid 22 was water. It can be seen from FIG. 6 that air permeability can be adjusted by selecting an appropriate ultrasonic vibration frequency and immersion time.
[0027]
When the porous metal sintered body 1 exhibits excessive air permeability after ultrasonic vibration, a predetermined amount of resin, for example, a silicone resin in a solvent such as toluene, is placed in the recess 31 through the passage 32 of the housing 30. Pumping and supplying the melted liquid, injecting the liquid from the outer peripheral surface 33 of the porous metal sintered body 1 into the pores 11, and ejecting the liquid that has passed through the pores 11 from the inner peripheral surface 2; In place of liquid, air is similarly injected into the pores 11 and ejected from the inner peripheral surface 2. Unnecessary liquid is ejected from the pores 11 together with air ejection, and after this drainage, a waste soaked with a solvent, etc. Thus, the liquid on the bearing surface 2 is wiped off, the porous metal sintered body 1 is dried at room temperature, and the resin injected into the pores 11 of the porous metal sintered body 1 is cured.
[0028]
By injecting the liquid in which the silicone resin is melted into the pores 11 in this way, the air permeability of the porous metal sintered body 1 can be reduced. The degree of reduction in air permeability depends on the concentration of silicone resin in the liquid. If you want to greatly reduce the air permeability, use a liquid with a high concentration of silicone resin and want to reduce the air permeability slightly. For this, a liquid having a low concentration of silicone resin is preferably used.
[0029]
An example of the relationship between the silicone resin concentration and air permeability is shown in FIG. As a solvent for dissolving the silicone resin, a mixed solution of toluene and ligroin was used. As the porous metal sintered body 1, one having an inner diameter of 50 mm, an outer diameter of 70 mm, and a length of 50 mm was used. The air permeability was expressed as a ratio of the flow rate after resin impregnation when the flow rate before resin impregnation was 100.
[0030]
According to the above method, as a result of immersing the porous metal sintered body 1 composed of the metal portion 13 and the inorganic portion 15 in the liquid 22 that is ultrasonically vibrated, first, the chips embedded in the pores 11. As a result, it is possible to eliminate clogging based on chips and abrasive grains, to eliminate indefinite air permeability due to chips and abrasive grains, and to disperse chips and abrasive grains in the environment of use. Therefore, it is possible to maintain a clean environment, and further, the weak part of the spread part (plastic flow part) 17 and the inorganic part 15 can be crushed to increase the opening area of the pores 11, and the porous metal sintered The air permeability of the body 1 can be adjusted without impairing the shape accuracy and surface roughness of the bearing surface 2 after grinding, and thus appropriate and stable air permeability can be easily obtained.
[0031]
In addition, although the above is an example in the case of manufacturing a cylindrical porous hydrostatic gas bearing, a plate-shaped porous hydrostatic gas bearing can be manufactured similarly.
[0032]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the porous hydrostatic gas bearing which can acquire appropriate and stable air permeability easily, and can remove simultaneously the chips and abrasives which were buried in the pore is provided. be able to.
[Brief description of the drawings]
FIG. 1 is a perspective view of a porous metal sintered body according to a preferred example of an embodiment of the present invention.
FIG. 2 is an explanatory view of an example in which the porous metal sintered body shown in FIG. 1 is inserted into a housing.
FIG. 3 is a copy of the porous metal sintered body shown in FIG. 2 when the inner peripheral surface (bearing surface) is enlarged with a microscope.
4 is an explanatory diagram in the case of enlarging the cross section of the inner peripheral surface side of the porous metal sintered body shown in FIG. 2;
FIG. 5 is an explanatory diagram of an example in which a porous metal sintered body is immersed in a liquid that is ultrasonically vibrated in a preferred example of an embodiment of the present invention.
FIG. 6 is a diagram showing the relationship between the immersion time of a porous metal sintered body in a liquid subjected to ultrasonic vibration and the air permeability.
FIG. 7 is a relationship diagram between a silicone resin concentration and air permeability of a porous metal sintered body.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Porous metal sintered compact 2 Inner peripheral surface 11 Pore 12 Opening 13 Metal part 15 Inorganic part 17 Extension part 22 Liquid

Claims (5)

  A step of preparing a porous metal sintered body obtained by mixing and sintering a metal powder and an inorganic powder; a step of grinding one surface of the porous metal sintered body to form a bearing surface; The step of immersing the formed porous metal sintered body in the ultrasonically vibrated liquid to increase the opening area of the pores of the bearing surface of the porous metal sintered body, and the ultrasonically vibrated liquid A step of injecting air into the pores after injecting a liquid in which a predetermined amount of resin is dissolved in a solvent into the pores of the porous metal sintered body after being immersed in Porous metal sintering, which determines the relationship between air permeability and air permeability for each ultrasonic vibration frequency, and selects the immersion time and the frequency of ultrasonic vibration and also selects the resin concentration to adjust the air permeability. A method for producing a porous hydrostatic gas bearing with adjusted body air permeability.   The method according to claim 1, wherein water, ethanol or an alkaline liquid is used as the liquid.   The method according to claim 1, wherein a silicone resin is used as the resin.   The metal powder contains at least tin, phosphorus, and copper, and the inorganic powder contains at least one of graphite, boron nitride, graphite fluoride, calcium fluoride, aluminum oxide, silicon oxide, and silicon carbide. 4. A method according to any one of claims 1 to 3.   The method according to claim 4, wherein the metal powder further contains nickel or manganese.

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