JPH0730795B2 - Method for manufacturing porous static pressure guide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) As one of means for achieving high speed and high accuracy of screw feed for converting rotary motion into linear motion, it is applied to a gap between a male screw and a female screw. There is a static pressure screw which supplies a pressure fluid and supports between a male screw and a female screw via fluid pressure. Further, there has been proposed a fluid bearing that supplies a pressurized fluid to a gap between a shaft of a rotating body and a bearing that supports the shaft. These are generally called static pressure guides. The invention thus relates to a method of manufacturing a porous hydrostatic guide.

(Problems to be Solved by the Prior Art and Invention) As is well known, the static pressure guide is a non-contact guide in which a pressurized fluid, for example, gas or fluid is supplied between the guide surfaces to levitate an object by fluid pressure. Not only the friction loss due to the movement of the object can be made extremely small, but also the guide surface is not worn at all. In addition, since the fluid also has the effect of averaging the machining accuracy of the guide surface, the guide accuracy is significantly improved.For example, ultra-high speed rotation and ultra-precision machining as a means to move an object at high speed and high accuracy over a long period of time. It has been used for measurement and measurement, or for mechanical element systems that require high-precision feed and positioning, such as guides for rotary bearings and linear guides, and has also begun to be applied to feed screws, further improving performance. Is desired.

Generally, in static pressure guide, one or more flow path resistances, that is, throttles, are provided in addition to the flow path resistance in the levitation gap formed between the guide surfaces instead of simply supplying the pressurized fluid between the guide surfaces. Small flow rate and floating rigidity between guide surfaces (hereinafter referred to as rigidity)
Devise so that

Generally, if the clearance between the male and female threads or the shaft and the bearing decreases, the fluid pressure in the clearance increases and the fluid pressure rises. Conversely, if the clearance increases, the fluid pressure decreases. Is configured to be maintained. The larger the rate of increase or decrease of the fluid pressure due to this clearance change, the higher the rigidity between the male screw and the female screw, or the shaft and the bearing, and the better the performance. However, since the rigidity cannot be increased so much only by the flow path resistance in the clearance, it is usual to add a flow path resistance such as a self-made throttle, a surface throttle, or an orifice throttle to efficiently increase the rigidity. It

In this case, the throttle plays an important role in the rigidity that governs the performance of the static pressure guide, so this throttle will be described first.

FIG. 4 is a cross-sectional view showing an example of a throttle in a conventional static pressure guide. (A) is a self-made throttle, (B) is an orifice throttle,
(C) is a surface diaphragm, (D) is a porous diaphragm, 1 is a floating body, 2 is an air bearing surface, 3 is a guide surface, 4 is a floating clearance, 5 is a supply hole, 6 is an orifice, 7 is a small groove, 8
Is a porous body.

The self-made throttle is a throttle in which the fluid passage is reduced in a spatial cross section formed in a portion directly below the air supply hole 5 in the floating clearance 4.

The orifice restrictor is provided with an orifice 6 having a minute hole at the center below the air supply hole 5 to serve as a restrictor.

The surface stop is a stop formed by processing a minute groove 7 having a minute cross section on the air bearing surface 2.

The porous restrictor is a restrictor that is a passage that is formed in the porous body 8 and that is composed of innumerable minute spaces.

In any case, the fluid pressurized and supplied with the original pressure Ps from the air supply hole 5 is once reduced to the intermediate pressure Pm by these throttles, and then inside the levitation gap 4, and finally when the pressure is further reduced, outside the levitation gap 4. Open to atmospheric pressure Pa. However, the total pressure in the levitation gap 4 is equal to the weight applied to the levitation body 1, and this is in balance. Therefore, the rigidity is the rate of change in the levitation clearance due to the increase or decrease in weight, and the source pressure Ps and the atmospheric pressure Pa are constant. Therefore, the larger the change rate of the intermediate pressure Pm with respect to the change in the levitation clearance, the greater the rigidity (inversely proportional to the levitation clearance). Get higher Since high-precision shape processing is an essential requirement for increasing rigidity, high rigidity reflects high-precision processing.

On the other hand, the self-made restrictor, the orifice restrictor, and the surface restrictor are all restrictors whose main purpose is to change the sectional area of the fluid passage. The difference from other diaphragms is that viscous resistance is added due to contact with the body wall.

Since this viscous resistance is proportional to the flow velocity, if the levitation clearance 4 is reduced in the porous throttle, the viscous resistance in the levitation clearance (inversely proportional to the cube of the levitation clearance) is naturally increased, and the inside of the porous body 8 is correspondingly increased. However, since the viscous resistance is proportional to the flow rate, the viscous resistance due to the porous restriction is rather reduced. Therefore, levitating gap 4
As a result, the fluid is supplied to the inside to raise the intermediate pressure Pm. On the contrary, if the floating clearance 4 increases, the intermediate pressure Pm is further lowered. This is the effect itself of increasing the rigidity. As described above, the porous restrictor is superior to other restrictors in that the static pressure guide has high rigidity due to the effect of viscous resistance.

Generally, in the static pressure guide, the higher the above-mentioned intermediate pressure Pm, the greater the load weight, and the intermediate pressure with respect to the change in the floating clearance.
The greater the rise and fall width of Pm, the higher the rigidity, but the intermediate pressure
Since Pm cannot exceed the original pressure Ps, if the intermediate pressure Pm is increased too much, rigidity cannot be obtained. For this reason, it is usual to find the ratio of the flow path resistance between the floating clearance and the throttle so that the peak value of the intermediate pressure Pm is about 2/3 of the original pressure Ps.

In this case, the smaller the levitation clearance, the higher the rigidity, which is advantageous. However, since it is necessary to keep the ratio of the flow path resistances constant, if the levitation clearance becomes smaller, the flow resistance of the levitation clearance will inevitably increase. Becomes Therefore, the throttle resistance of the static pressure guide can be increased by this amount, and the absolute value of the clearance variation corresponding to the load weight can also be reduced, resulting in a static flow guide with a small flow rate and high rigidity, but minimizing the floating clearance Since it depends on the technology, it is well known that the improvement of the performance of the static pressure guide is closely related to the improvement of the high precision processing technology.

The conventional problems in the porous diaphragm will be described below.

FIG. 5 shows a sectional view of the pressure-supplied structure using a thick film porous body, in which 1 is a floating body, 2 is an air bearing surface,
3 is a guide surface, 4 is a floating clearance, 5 is an air supply hole, 9 is a pressure supply port, 10 is an opening port, 11 is a sealing surface, and 12 and 13 are arrows A and B, respectively, which are porous. The flow direction, position, and flow rate of the fluid in the body 8 are indicated by the arrow direction, position,
And corresponding to the size. In FIG. 5, the fluid tries to flow from the pressure supply port 9 toward the opening port 10 so that the flow path resistance is minimized. In this case, the thicker the porous body 8 is and the wider the width of the pressure supply port 9 is, the more the fluid flows through the arrow A1.
As shown by 2, the flow concentrates on the flow opening 10, and the flow in the central portion indicated by the arrow B13 is reduced accordingly.

FIG. 6 shows a sectional view of a pressure-supplied structure using a thin film porous body. In the figure, 1 is a floating body, 2 is an air bearing surface,
3 is a guide surface, 4 is a floating clearance, 5 is an air supply hole, 9 is a pressure supply port, 10 is an opening port, 11 is a sealing surface, 13 is an arrow B, 14 is an arrow C, and 15 is an arrow D. Indicates the flow of fluid. Sixth
Also in the figure, since the fluid tries to flow so that the flow path resistance is minimized, the thinner the porous body 8 is and the narrower the width of the pressure supply port 9 is, the fluid does not pass through the levitation gap 4 and inside the porous body 8. Flow through arrow C14 and arrow D15, again arrow B1
The flow in the central part shown in 3 becomes smaller.

As described above, in the case of a simple porous diaphragm, the width of the pressure supply port 9 and the porous body 8
It has been stated that even if the thickness of the above is devised, the fluid bypasses the vicinity of the central portion of the levitation gap 4 and concentrates in the vicinity of the opening 10. On the other hand,
The sum of the flow path resistances is the sum of the flow path resistances of the porous part and the levitation clearance part, and the intermediate pressure Pm is determined by the difference of the flow path resistances. With a small flow rate, the rising / falling width of the intermediate pressure Pm, that is, the rigidity can be increased. Therefore, without depending on the levitation gap 4 near the opening 10,
A pressure-supplied structure in which the fluid flows over a longer distance in the levitation gap 4 is desirable. For this purpose, it is sufficient to increase the flow path resistance particularly on the air bearing surface 2 of the porous body. A texture stop is used.

FIG. 7 is a cross-sectional view of a conventional pressure-supplied structure in a crushed porous body, where 1 is a levitation body, 2 is an air bearing surface, 3 is a guide surface, 4 is a levitation clearance, 5 is an air supply hole, and 9 is a pressure supply port. , 10 is open mouth, 11
Is a sealing surface, and 12 and 13 are arrows indicating the flow of fluid. Reference numeral 16 indicates a meshing layer on the air bearing surface 2, and 17 indicates a flow of fluid by an arrow E.
In FIG. 7, a crush layer is formed from the inside of the porous body 8 by crushing.
Since the flow path resistance of 16 becomes sufficiently large, the inside of the porous body 8 has a substantially uniform pressure close to the original pressure Ps. Therefore, even if the fluid flows inside the porous body 8 as indicated by arrow A12, the fluid flows out almost uniformly from the crushed air bearing surface 2 as indicated by arrow E17. Therefore, as compared with a uniform porous body, a large amount of fluid flows over a long distance in the levitation skimmer 4 near the center indicated by an arrow B13, and accordingly, it is possible to realize a porous throttle that can obtain high rigidity with a small flow rate. Become.

As mentioned above, it has been explained that the porous restrictor is superior to the conventional restrictor, and that the addition of the surface restrictor to the porous body provides a guide with a smaller flow rate and higher rigidity. The conventional surface drawing technique will be described below.

As a conventional technique, as described above, a method of reducing the passage cross-sectional area of the fluid in the surface layer of the porous body by crushing is adopted. The reason for this is closely related to that the conventional porous material is mainly composed of a metal material. That is, in the porous body obtained by firing and bonding the particles of the metal powder at a temperature below the melting point, the innumerable spaces between the particles are used as fluid passages. This is because a wide variety of materials can be obtained relatively easily and inexpensively because they are practically used as materials for filters and filters.

The crushing in the metallic material porous body utilizes plastic deformation of the metal, and specifically, cutting or grinding processing conditions, for example, the sharpness of the cutting edge of the processing tool, the cutting amount, the processing speed,
Alternatively, by selecting a processing temperature or the like for processing, the cross-sectional area of the fluid passage existing on the surface of the porous body is reduced in the surface layer by plastic deformation. Therefore, the amount of plastic deformation corresponds to the increase in the flow path resistance of the surface layer. However, since there are innumerable large and small holes on the surface of the porous body, naturally small holes are sealed if the amount of plastic deformation increases, and semi-sealed holes and holes that are not so sealed are stochastically left behind. Will be done.
This is the principle of surface layer drawing by crushing, and attempts to control the flow path resistance of the surface layer of the porous body by the amount of plastic deformation. However, crushing due to plastic deformation is limited to materials that can be plastically deformed, and it is of course necessary to select processing conditions, and the characteristics of porous materials, such as variations in sintering strength and hardness, adversely affect processing conditions. There are drawbacks such as tool friction and damage, stable securing of machining conditions, poor reproducibility and productivity, and plastic deformation itself based on stochastic machining, which hinders realization of a proper and uniform crushed surface. I have many. In particular, if the amount of plastic deformation approaches the particle size of the powder that makes up the porous body, the particles will drop off and re-adhere at the same time, and the wear and damage of the processing tool will become severe, so accurate control of the amount of crushing is expected. However, it is inevitable that the machining accuracy of the blind surface will be significantly reduced. in this way,
Plastic deformation is an element that contradicts the improvement of machining accuracy,
As mentioned above, since the performance of the static pressure guide itself is directly connected to the improvement of the machining accuracy, it can be said that the crushing due to the plastic deformation is a surface layer drawing technology which goes against the high performance of the static pressure guide.

On the other hand, the blinding significantly changes the flow path resistance of the porous body. However, in order to secure the rigidity of the static pressure guide, it is necessary to set the flow path resistance ratio so that the peak value of the intermediate pressure Pm is about 2/3 of the original pressure Ps, as described above. It is required not only to uniformly crush the surface of the body but also to control the flow path resistance of the entire porous restrictor. Therefore, it is no exaggeration to say that the quality of the blindness determines the performance of the static pressure guide. However, in reality, there are almost no examples where the porous throttle is put to practical use, and the conventional throttle, particularly the surface throttle, is the mainstream of static pressure guide. This itself shows that the technology for controlling the flow path resistance that causes the porous throttle to manifest itself, or the addition of the surface layer throttle is unsolved.

(Object of the Invention) The present invention has been proposed in order to improve the above-mentioned drawbacks, and an object thereof is to provide a method for manufacturing a porous static pressure guide provided with a new flow path resistance control means.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention, in the manufacture of a static pressure guide including a levitation body and a fixed body, forms the levitation body with a porous ceramic body, A step of immersing a first area on the surface of the floating body in a plating solution, and sucking the plating solution from a second area other than the first area on the surface of the floating body through the floating body while controlling the suction pressure of the plating solution. By doing the first
And a step of forming a coating on the surface of the porous ceramic and the inside of the porous ceramic, and then subjecting the porous body to precision processing up to the plating base to produce a porous static pressure guide. A method is the subject matter of the invention.

(Example 1) First, electroless plating will be briefly described.

As is well known, in electroplating, metal cations in the electrolytic solution themselves are guided to and adhere to the cathode by the action of an external current, but electroless plating in a broad sense reduces metal cations in the electrolytic solution regardless of the external current. It is also a generic term that includes all the plating methods for depositing the metal and is sometimes called chemical plating.

The feature of electroless plating is that metal cations in the electrolytic solution are reduced and deposited without relying on an external current.However, this method uses a potential difference unique to different metals, for example, substitutional zinc plating or immersion. Like gold plating, the cation of a high potential metal (noble) is brought into contact with a low potential metal (base),
The method of depositing the precious metal by reducing and depositing it, and utilizing the reducing action based on the oxidation or decomposition reaction of the reducing agent, for example, chemical copper plating or electroless nickel (Ni) plating It is roughly classified into a method of acting as a catalyst to reduce metal cations in the electrolytic solution, and depositing and depositing a metal on the surface thereof. However, the reduction method plays an important role industrially today.

As described above, the electroless plating is based on the chemical reaction on the surface of the object to be plated, so that the adhesion does not concentrate at the place where the electric field strength is high like the electroplating, and the plating can be performed to an extremely uniform thickness, and It has characteristics different from electroplating, such as being able to plate even in a place where an electric field cannot exist, for example, in a porous body.

As mentioned above, it has been explained that there are various methods even if it is simply referred to as electroless plating, but electroless nickel plating of the reduction method as a flow path resistance control means of the porous body is particularly suitable among them, so Examples will be described.

FIG. 1 shows an example of electroless nickel plating (hereinafter referred to as Ni plating) used in the present invention, in which 18 is a porous body to be plated, and 19 is a porous body 18 to be plated. A holding tool, 20 is a beaker containing the Ni plating solution 21, 22 is a thermometer, 23 is a water temperature type constant temperature bath, 24 is a heater for heating water, 25 is a propeller type agitator, and 26 is a pipe 27. Negative pressure tank 28 connected to the holder 19 and the vacuum pump 29 is a negative pressure manometer. Further, 30, 31, and 32 are a flow rate adjusting valve, an opening / closing valve A, and an opening / closing valve B, respectively, which are provided in the pipe 27, and 33 is an opening / closing valve C. These valves are used when controlling the flow rate of the Ni plating liquid flowing in the pipe line 27 and when treating the waste liquid in the negative pressure tank 26.

Since it has such a structure, the temperature of the Ni plating solution 21,
In addition, the flow rate of the Ni plating liquid flowing inside the porous body 18 can be freely manufactured. Therefore, once the inside of the porous body 18 is replaced with water, the flow rate adjusting valve 30 is closed and the porous body 18 is added to the plating solution, and the Ni plating solution 21 enters the porous body 18. Is only diffuse. In this case, the more the Ni cations in the plating solution penetrate, the more they adhere to the wall surface inside the porous body 18 and decrease, so that the plating is limited to only the surface layer portion of the porous body 18, and finally. Innumerable holes existing on the surface of the porous body 18 are sealed. On the other hand, if the flow rate adjusting valve 30 is opened and plating is performed, a new plating solution containing Ni cations is constantly replenished inside the porous body 18, so that the deep layer inside the porous body 18 can be plated. Become. Therefore, the flow rate of the plating solution is the negative pressure in the negative pressure tank 26 and the flow rate adjustment valve 30.
The plating speed can be controlled by the temperature of the Ni plating solution 21, and the plating amount can be controlled by time. Therefore, if the relationship between the plating amount and the flow path resistance of the porous body is obtained in advance, the plating amount can be predicted, and in some cases, it is possible to perform plating while measuring the flow path resistance during plating. .

As an effect of these, it is possible to accurately control the flow path resistance of the porous body, it is possible to increase the flow path resistance in the surface layer portion, it is also possible to control in the deep layer portion, so that the control range of the flow path resistance is expanded by this amount, Alternatively, since sealing can be performed on the surface of the porous body, the sealing surface can be selectively formed on the porous body by masking the surface that does not require sealing. Controllability of
In addition to expanding the control range, new effects will also be produced.

Further, by adjusting the flow rate of the plating solution, it is possible to gradually change the degree of plating adhesion from the surface layer to the deep layer of the porous body. Also, this is a holder 19
On the other hand, if the front and back of the porous body 18 are set upside down, it is possible to prepare a material having plating attached to the deep layer as well as the surface layer.

Needless to say, deep layer plating is almost impossible with ordinary electroplating. Especially Ni plating is excellent in that it is not corrosive.

(Example 2) Next, the form of adhesion of Ni plating to the porous body will be described.

FIG. 2 shows a cross-sectional structural model of a sintered porous body, in which 34 is a sintered particle, 35 is a particle bonding portion between the sintered particles 34, 36 is a void of the sintered particle 34, That is, a fluid passage. Further, FIG. 2 (A) is a cross section passing through the center of the sintered particles 34, and FIG. 2 (B) is a cross section passing through the particle bonding portion 35 of the sintered particles 34, which are cross-sectional structures when cut. Thus, since the area occupied by the fluid passage 36 differs depending on the cross-sectional position, it can be said that the porous body is finally constituted by a fluid passage in which gourds are connected in three dimensions. However, in order to facilitate understanding, FIG. 2 shows a structure in which spherical sintered particles 34 having the same diameter are arranged in an orderly manner, but actually, the sintered particles 34 having different shapes and sizes are randomly arranged. It is a structure and the uniform fluid passage is not always formed in the porous body,
This means that fluid passages of different sizes are mixed.

On the other hand, when constructing a static pressure guide, if a conventional throttle can be designed, a throttle with a desired flow path resistance can be manufactured by precision processing if it can be designed, but a porous throttle has a degree of freedom in selection of the sintered particle 34 diameter and uniform. It is not easy to obtain the desired flow path resistance because the porous material itself has a unique manufacturing technology. Therefore, as described above, it is necessary to use the existing porous material to control the flow path resistance to a desired flow path resistance by some means, and also to obtain the flow path resistance control means that particularly increases the throttling resistance in the surface layer portion. .

FIG. 3 shows an example of a cross-sectional model of a porous squeezing shape plated with Ni according to the present invention. 37 is a thicker fluid passage caused by unevenness of the porous body, and 38 is a similarly thinned fluid passage. , 39 is the inflow side of the plating solution, 40 is the outflow side, 41 is the deep-layer plating film deposited by increasing the supply rate of the plating solution into the porous body, and 42 is adhered by reducing the supply rate of the plating solution. It is the surface layer plating film which was made to do.

As described above, the flow rate of the plating solution passing through the porous body is controlled by the pressure difference between the inflow side 39 and the outflow side 40, but in this case, the plating solution has a resistance regardless of the deep layer and the surface layer plating. Since it flows in the porous body to the minimum, the plating solution naturally concentrates in the thick fluid passage 37 with low resistance, so the thick fluid passage 37 is plated to a deeper layer, and the thin fluid passage is formed. The plating on 38 is limited to the surface layer, and as a result, the flow path resistance in the porous body is made uniform. However, as a result of the plating liquid being uniformly supplied to the flat portion on the surface of the porous body, the deposited film thickness becomes constant, so that the processing accuracy before plating is secured.

In addition, as is well known, the Ni-plated film itself is a hard film that is highly resistant to corrosion, abrasion and lubrication, and is a film that is unlikely to undergo plastic deformation. Therefore, even after the plating, the surface of the porous body can be highly accurately processed by grinding or abrasive grain processing. In particular, if a ceramic material such as alumina (Al ₂ O ₃ ), silicon nitride (SiN), or silicon carbide (SiC) is used as the porous material, the porous body itself does not allow plastic deformation. Since ultra-precision machining up to the plating underlayer using a diamond tool can also be realized, the performance of the static pressure guide, which is directly linked to the improvement of machining accuracy, can be greatly improved compared to the conventional one.

(Effects of the Invention) In the static pressure guide, the contact surface between the floating body and the fixed body is originally
It must be strong and have a smooth surface. However, even if the floating body is simply metal-plated, even if it is a Ni-plated film excellent in corrosion resistance, wear resistance, and lubricity, it is inferior to a smooth ceramic body.
However, when the base is made of a porous ceramic body as in the present invention, since the porous ceramic body is a material that does not allow plastic deformation at all, it is necessary to remove the plating film on the surface of the porous body after plating. "Precision processing up to the plating base" is also possible, and after plating, the porous ceramic body can be exposed on the contact surface of the floating body.

Then, while the porous "holes" are deeply plated, the porous body is made of a strong ceramic, so it can withstand ultra-high speed, has high rigidity, and enables highly accurate positioning. It is possible to obtain an excellent static pressure guide having a large floating body.

[Brief description of drawings]

FIG. 1 is an embodiment of electroless nickel plating of the present invention, FIG. 2 is a sectional structure model of a sintered porous body, and FIG. 3 is a cross section showing a shape of a porous drawing to which electroless nickel plating of the present invention is applied. A model, FIG. 4 is a cross-sectional view showing an example of a restriction in a conventional static pressure guide, FIG. 5 is a cross-sectional view of a pressure-feeding structure using a thick film porous body, and FIG. 6 is a thin film porous body. FIG. 7 shows a sectional view of the pressure-supplied structure in the case of using the above, and FIG. 1 ...... Floating body 2 ...... Floating surface 3 ...... Guide surface 4 ...... Floating skimmer 5 …… Air supply hole 6 …… Orifice 7 …… Small groove 8 …… Porous body 9 …… Pressurizing port 10 …… Open Mouth 11 ...... Sealing surface 12 ...... Arrow A 13 ...... Arrow B 14 ...... Arrow C 15 ...... Arrow D 16 ...... Blinding layer 17 ...... Arrow E 18 ...... Porous body to be plated 19 ...... Retainer for porous material 20 …… Beaker 21 …… Ni plating solution 22 …… Thermometer 23 …… Water temperature constant temperature bath 24 …… Heater 25 …… Propeller type agitator 26 …… Negative pressure tank 27 …… Pipe Passage 28 …… Negative pressure gauge 29 …… Vacuum pump 30 …… Flow control valve 31 …… Opening valve A 32 …… Opening valve B 33 …… Opening valve C 34 …… Sintered particles 35 …… Particle joint 36 …… Vacuum 37 …… Thick fluid passage 38 …… Thin fluid passage 39 …… Plating solution inflow side 40 …… Plating solution outflow side 41 …… Deep layer plating film 42 …… Surface layer plating film

Claims (1)

[Claims] 1. A method of manufacturing a static pressure guide comprising a levitation body and a fixed body, wherein the levitation body is formed of a porous ceramic body, and the first region on the surface of the levitation body is immersed in a plating solution, From the second area other than the first area on the surface of the float,
A step of forming a coating film on the surface of the first region and inside the porous ceramic by suctioning the plating solution through the floating body while controlling the suction pressure of the plating solution; and A method of manufacturing a porous static pressure guide, comprising the step of performing precision processing up to the base.