JPS62274154A - Static pressure screw and its manufacture - Google Patents

Abstract

PURPOSE:To eliminate the need of working a hole, a groove and the like on a flank surface by using a porous body for a fluid supply path confronting with the flank surface of a static pressure screw in the static pressure screw supporting between a male screw and a female screw out of contact by fluid pressure. CONSTITUTION:A nut stored in a case 2 fixes a porous body 11 made of ceramics or the like on a screw base 20 and further the forward end portion 19 made of the same material as that of the base 20 thereon, and forms a screw clearance 8 between a flank surface 9 and a male screw. Further there are provided a connecting hole 12 for supplying fluid pressure from a supply groove 4 of the base 20 to the porous body 11 and a reclaiming hole 7 for reclaiming a fluid from a screw valley portion of the nut to a reclaiming groove 5. In this arrangement, the porous body functions as a passage resistance, and the porous body itself works as a passage, so that it is necessary to work a supply hole and a passage groove on the flank surface so as to easily obtain a static pressure screw, the angle of thread of which is vertical and a static pressure screw made of ceramics.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a static pressure screw that supports a male thread and a female thread without contact using fluid pressure.

[Conventional technology]

As one means of achieving high speed and high precision screw feeding that converts rotation into linear motion, pressurized fluid is supplied to the gap between the male thread and the female thread (hereinafter referred to as the thread gap), and the male thread is There is a static pressure screw that supports the female thread without contact.

This static pressure screw has a complicated internal thread structure for fluid supply and recovery, and there are many technical issues such as not being easy to design or requiring high-precision machining. Frictional loss, which is the main cause of problems, can be extremely reduced, and wear can be completely eliminated. In recent years, it has been applied to manufacturing equipment that requires high speed and high precision, such as ultra-precision processing, semiconductor elements, optical elements, and electronic equipment. is being considered.

Figure μ shows a cross-sectional view of the structure of a conventional static pressure screw.

Male thread / is a normal lead screw. On the other hand, female threads have a complicated structure because they supply and collect fluid into the thread gap. That is, it is composed of a case 2 and a nano nut 3, and the cylindrical outer circumference of the nut 3 has a fluid supply groove and a collection groove! is carved in a spiral shape to match the pitch of the male thread, and the supply groove and recovery groove! is guided to the supply hole 2 and the recovery hole 7, and the fluid is supplied and recovered to the screw gap ♂. Case 2 has fluid supply and
There is a recovery hole 2/.

FIG. 5 is an enlarged sectional view of the threaded portion. Conventional static pressure screws have slopes between the crests and valleys of the screw (hereinafter referred to as flank surfaces),
That is, a trapezoidal screw in which the angle of the thread between the left and right flank surfaces 2 is around zO0 is mainly used. The reason for this is that when machining the supply hole B that guides the fluid from the supply groove≠ to the thread gap r, if the flank surface is not inclined, that is, if the angle of the thread is vertical, the supply hole B This is because the machine must be machined at an angle, which is extremely difficult and almost impossible in terms of processing technology. In addition, since the recovery hole 7 is simply a passage for fluid, it may be located anywhere other than the flank surface, for example, in the valley of a female thread, and does not require much precision in machining, but the supply hole 6 has a flank surface. Since they are present on the left and right sides of the thread, more than twice the number of recovery holes 7 must be machined. Furthermore, since the supply hole 2 directly affects the uniformity of the band and flow of the fluid supplied to the screw gap ♂ and controls the performance of the static pressure screw, precision in machining is required. In particular, when downsizing the static pressure screw, the supply hole B also becomes relatively thin, making precision machining even more difficult, which has the drawback that it is not easy to downsize the static pressure screw.

On the other hand, hydrostatic screws also follow the same principle as hydrostatic bearings.
When the gap between the male thread and the female thread, or between the shaft and the bearing, decreases, the flow path resistance within the gap increases, causing the fluid pressure to rise, and conversely, as the gap increases, the fluid pressure decreases.With this balance, a certain screw gap or bearing gap is maintained. configured to be maintained. The greater the rate of increase or decrease in fluid pressure due to this gap change, the greater the rigidity between the male thread and the female thread, and between the shaft and the bearing.
This means that the performance will be good. However, it is not possible to increase this rigidity very much with only the flow path resistance in the gap, so it is usually necessary to add flow path resistance such as self-control, surface restriction, orifice restriction, etc. to efficiently increase the rigidity. be done. However, if an orifice restriction is applied to a static pressure screw,
Furthermore, machining of the supply hole B is difficult, so self-drawing and surface drawing are often used.

FIG. 6 is a flank surface of a self-drawn type static pressure screw viewed from the screw feeding direction. It is twisted in a spiral shape in a direction perpendicular to the plane of the paper, but the cut surface is not shown. Self-control is a method in which the change in the cross-sectional area of the flow path from the supply hole 2 to the screw gap is used as the flow resistance. Most of the flow flows in the radial direction of the flank surface so that the flow is minimized.

Therefore, in order to supply fluid evenly to all parts of the circumference of the flank surface, it is necessary to machine a large number of supply holes on the flank surface that require precision machining, resulting in the high cost of static pressure screws. This is the biggest drawback that leads to

FIG. 7 shows the flank surface of the surface drawing type. Similar to FIG. 6, the cut plane is not shown. The surface aperture is such that a channel groove 10 is provided on the flank surface, and a change in the cross-sectional area of the channel from the channel groove 10 to the screw gap is used as the channel resistance. in this case,
Since the channel groove 10 is provided in the circumferential direction of the flank surface, the fluid discharged from the supply hole 2 reaches the flank surface (screw gap) after flowing through the channel groove 10 with low flow resistance.

For this reason, it is not necessary to machine a large number of supply holes 2 as in the case of Jikado drawing, but since it is not easy to get someone to the processing position of the processing tool, precision is required on the flank surface of the female screw like the supply hole. The formation of the flow passage groove 10 itself is a drawback that increases the cost of the hydrostatic screw.

[Problem that the invention seeks to solve]

An object of the present invention is to realize a static pressure screw that can be configured without providing a supply hole or a flow path groove on the flank surface of the static pressure screw, and to provide a small, high-performance, low-cost static pressure screw.

[Means for Solving the Problems] The static pressure screw according to the present invention is constituted by a porous body having at least a part of its flank surface having a fluid supply passage, and a conduction for supplying fluid into the porous body. The method for producing a static pressure screw according to the present invention is characterized in that the hole is connected to the porous body, and the method for manufacturing a static pressure screw according to the present invention includes a tubular base material in which at least a porous hollow cylinder is fixed to the inside of a multi-ring cylinder. forming threads and thread valleys so that at least a portion of the flank surface is made of the porous body; and a step of machining the tubular base material from the outside to form a through hole reaching the porous body. It is characterized by including the step of forming.

[For production]

In the present invention, by using a porous body in the fluid supply path to the flank surface of the static pressure screw, the porous body acts as a flow path resistance. In addition, since the porous material itself becomes a flow path,
There is no need to process supply holes or channel grooves on the flank surface. Furthermore, it is now possible to easily create static pressure screws with vertical thread angles and ceramic static pressure screws, which was nearly impossible in the past. In addition, the static pressure screw can be made smaller.

〔Example〕

(Example/) FIG. 1(a) shows a first example of the present invention, where // is a porous body and /λ is a communication hole between the supply groove≠ and the porous body 77.

In the figure, the same numbers are used for the same parts as in the conventional example.

/9 is the tip of the thread, which is made of the material of the inner ring shown in Fig. 3 (a), which will be described later, and -〇 is the base of the screw, and is made of the material of the outer ring shown in Fig. 3 (a), which will be described later. /6 materials. The fluid passes through the through hole /2 from the supply hole, reaches the porous body //, and is then supplied to the left and right screw gaps ♂.

Further, FIG. 1(b) schematically shows the vicinity of the flank surface of the static pressure screw in FIG. 1 as viewed from the screw feeding direction. Although it is twisted in a spiral shape in a direction perpendicular to the plane of the paper, this cut surface is not shown. Note that the conductive hole /2 located behind the flank surface is shown by a broken line. The conductive hole/2 is located at a position corresponding to the ridge.

Normally, a porous body// is composed of a countless number of continuous micro-spaces, so the fluid passing through it is affected by flow resistance due to changes in cross-sectional area and flow paths due to viscous friction with the walls of the micro-spaces. It will be met with resistance. For this reason, the cross-sectional area change becomes a superior flow path resistance compared to self-restriction or surface restriction, in which the main flow path resistance is a change in cross-sectional area. In other words, the flow rate of fluid is proportional to the cube of the screw gap or bearing gap, and the viscous resistance is proportional to the flow velocity or flow rate.The flow path inside the porous material is extremely thin and has viscous resistance, so the porous restrictor has a large screw gap. As the flow rate increases, the viscous resistance within the porous material increases, so unless the flow rate is increased, the screw gap will become smaller, and if the flow speed decreases, the viscous resistance within the porous material will decrease, which will act to prevent the flow rate from being reduced. This means that, compared to a conventional diaphragm that only changes cross-sectional area, a porous diaphragm that has viscous resistance in addition to a change in cross-sectional area will reduce the pressure in the gap more as the gap increases, and as the gap decreases, the pressure in the gap will decrease more. This has the effect of increasing pressure. This improves the M property of the static pressure screw compared to the conventional one.

Because of this structure, in the static pressure screw of the present invention, the porous body serves both as a fluid supply path and as an addition of flow path resistance. This effect eliminates the need for precision machining of supply holes and flow channel grooves, which are essential for self-drawn and surface-drawn type static pressure screws, making machining easier and making it possible to lower the price of static pressure screws. In addition, conventional static pressure screws required supply holes to be provided on the left and right flank surfaces of the screw thread, but the hydrostatic screw of the present invention has 7 conduction holes/2 on the left and right flank surfaces. can supply fluid to In addition, since this conduction hole /2 is provided in a place that is not used effectively even in conventional static pressure screws, the screw thread can be made smaller by the amount that does not require the supply hole B, and the size of the static pressure screw can be reduced. It becomes possible.

It should be noted that the static pressure screw of the present invention can be used with either gas or liquid, and the viscosity of gas and liquid is greatly different, so a porous material with appropriate flow resistance should be selected accordingly. Needless to say, it's good. The proper flow rate of fluid depends on the ratio of thread clearance to porous volunty. By increasing the gap, the porosity is controlled to a smaller value, and by decreasing the gap, the porosity is controlled to a smaller value, thereby achieving an appropriate design value. Porosity can be adjusted, for example, by adjusting the particle size of the raw material before sintering.

(Embodiment 2) Figure 2 shows a second embodiment of the present invention. It is nearly impossible to provide a supply hole in a conventional static pressure screw unless the flank surface is oblique, but the static pressure screw of the present invention does not require a supply hole, so the screw shown in Fig. 7 A static pressure screw with vertical crest angles can be easily realized.

In general, screws with inclined threads have many advantages, such as being able to receive loads in the direction perpendicular to the feed, the flank surface acting as a guide for the feed, and having automatic centripetal properties. The machining method for creating threads has a drawback in terms of accuracy, and since machining is mainly done using a mold formed on the threads, it is not easy to form flank surfaces with high precision. As the machining force component becomes large, in machining the male screw that determines the feed accuracy of the screw, a bending moment component acts and induces deflection of the male screw, impeding high-precision machining. In this regard, screws with vertical thread angles have exactly the opposite advantages and disadvantages, and are less prone to deflection during machining. A trapezoidal screw with a vertical angle is used. The static pressure screw of the present invention has a vertical screw thread angle as in this embodiment, and can more easily achieve high precision screw feeding, which is the main purpose of a static pressure screw. However, it is needless to say that the static pressure screw of the present invention can be applied to a wide range of applications since the angle of the screw thread need not be particularly limited to vertical and can be freely selected.

In addition, in FIGS. 1 and 2, the porous body // is provided in a part of the crests and valleys of the screw, but the porous body may be provided entirely between the crests and troughs of the screw.

Further, the conduction hole /2 only needs to reach the porous body //, and does not need to be opened in the porous body. It goes without saying that various changes may be made without departing from the spirit of the claimed invention.

(Embodiment 3) FIGS. 3(a), 3(b), and 3(C) show a third embodiment for explaining the method of manufacturing a static pressure screw of the present invention. Third
Figure (a) shows the manufacturing process of the processed base material /3 constituting the nut portion of the hydrostatic screw of the present invention, /≠ is a porous hollow cylinder, /Y is the inner ring cylinder, /2 is the outer ring cylinder. Processing base material /3 is a porous hollow cylinder /4t, and inner cylinder /! Arrange and integrate the outer ring cylinder/B so that they are coaxial. Integration is an individually manufactured inner cylinder/! , a method of fitting the outer ring cylinder/2 and the porous hollow cylinder/Hiro and then joining them by thermal diffusion;
A method in which a porous material is injected into the gap between the inner cylinder/J'' and the outer cylinder/2 and then fired, or a rear inner cylinder in which a porous part is formed by plasma spraying on the outer surface of the inner cylinder/J- or the inner surface of the outer cylinder. Various methods can be applied, such as the method of fitting and joining /! or outer ring cylinder /O.In addition, the processing base material /3 (from /Hiromi or /G to /&) may be made of porous material such as metal or ceramic. Any object that has a body is fine.

Figure 3 (bl is the processed base material manufactured in this way/3
Then, a female thread part /7 is manufactured by a known cutting process and a grinding process, and a fluid supply groove ≠ and a discharge groove j are created in a spiral shape by cutting or grinding process, and a through hole /2 and a discharge groove are formed by drilling. The nut/♂ of the hydrostatic screw of the present invention with hole 7 made therein is shown.

FIG. 3(C) shows the NAND/♂ of the present invention assembled into the case 2 by press-fitting or shrink-fitting. Because this manufacturing method is used, there is no need to manufacture a large number of precise supply holes and flow grooves as in the past, and only the flank face of the screw, which is unavoidable since it is a static pressure screw, requires precision machining. As a result, the influence of machining accuracy on performance can be reduced, and machining is also easy, making it possible to improve the performance and lower the cost of static pressure screws. In addition, in conventional static pressure screws, the material of the nut/♂ was limited to metal due to precision machining of the supply hole and flow channel groove, but the machining base material/3 is made of ceramic, and the nut is made of ceramic during the pre-firing stage. After preparing the form of the static pressure screw of the invention, it is possible to carry out final firing using normal machining, and finally grinding or lapping only the flank surface of the screw with high precision, making it possible to create a ceramic static pressure screw. It will be possible. Compared to metals, ceramics are suitable for high-precision machining due to their high rigidity and low machining distortion, and since they do not undergo plastic deformation, there is no need to worry about clogging of porous bodies due to machining. It is an advantageous material for realization. Furthermore, it goes without saying that it is a material that has a low coefficient of thermal expansion, is lightweight, and meets the main objectives of static pressure screws: high speed and high precision.

Although the embodiment shown in FIG. 3 has been described with an inner ring cylinder, it is possible to manufacture the static pressure screw shown in FIG. 3(C) even without an inner ring cylinder.

〔Effect of the invention〕

As explained above, the porous drawing type static pressure screw of the present invention shown in Examples/2 is equipped with precise supply holes and flow channels that are essential for conventional self-drawing and surface drawing type static pressure screws. Since it does not require the processing of grooves, it is not only easy to process, but also has a wide range of applications because the angle of the thread can be selected.

In particular, the realization of a screw with a vertical thread angle, which was nearly impossible in the past, can further improve the precision of screw feeding, which is the main purpose of static pressure screws. Also, 7 pieces)
There is no need to provide a supply hole, and it is sufficient to provide seven through holes for each screw thread (seven for each flank surface on both sides), so the screw can be easily miniaturized. In addition, porous orifices are superior to conventional orifices in that they can automatically control the flow rate, so they are effective in increasing the rigidity of hydrostatic screws, making them smaller, with higher performance, and at lower prices. There are various advantages that are directly connected to

The method for manufacturing a hydrostatic screw of the present invention shown in Example 3 has the advantage that a processed base material for a porous drawn-type hydrostatic screw can be obtained relatively easily by various methods. This has the advantage of making it possible to increase the speed and precision of screw feeding by taking advantage of the characteristics of ceramics.

Therefore, precision feeding of samples and processing/measuring tools in equipment that requires ultra-precision processing or measurement accuracy, high-speed and precision drive of XY stages used for fine pattern transfer and inspection in semiconductor device manufacturing processes, and optical and magnetic disk devices The characteristics of the static pressure screw of the present invention can be utilized for high-speed, high-precision feeding and positioning of writing and reading heads.

Furthermore, in Examples/and 2, a case was explained in which a part of the flank surface of the female thread is made of a porous material, but a part of the flank surface of the male thread is made of a porous material, and fluid conduction is provided to the male thread side. It is also possible to provide holes.

In addition, in Examples/Example C, an example in which a part of the flank surface is made of a porous material has been described, but the whole part up to the tip of the thread may be made of a porous material. In that case, it is sufficient to use a tubular base material having a double structure without an inner ring/tube as shown in FIG. 3(a).

[Brief explanation of drawings]

Fig. 1(a) is a sectional view of the first embodiment of the static pressure screw of the present invention using a porous orifice, Fig. 1(b) is a flank surface of the embodiment, and Fig. 2 is a porous orifice. FIG. 3 is a sectional view of a second embodiment of the hydrostatic screw of the present invention using a porous aperture, and FIG.
Figure ≠ is a sectional view showing the structure of a conventional static pressure screw. The figure is an enlarged sectional view of the threaded portion in Fig. µ, Fig. 2 is a flank face of a conventional static pressure screw with a self-drawn type, and Fig. 7 is a flank face of a face drawn type in a conventional static pressure screw. / is a male thread, 2 is a case that stores the nut, 3 is a nut, ≠ is a supply groove, ≠ is a collection groove, O is a supply hole, 7 is a collection hole,
♂ is the thread gap, ri is the flank surface, 10 is the flow groove, // is the porous body, /2 is the through hole, /3 is the processed base material, /Hiro is the porous hollow cylinder, /yo is the inner ring cylinder, /2 is the outer cylinder, /7 is the female thread, /♂ is the nut, / is the tip of the thread, -0 is the base of the screw, and 2/ is the fluid supply/recovery hole in the case.

Claims (2)

[Claims] (1) At least a part of the flank surface is composed of a porous body having a fluid supply path, and a conduction hole for supplying fluid into the porous body is connected to the porous body. Characteristic static pressure screw. (2) A tubular base material with at least a porous hollow cylinder fixed to the inside of the outer ring cylinder is machined from the inside, and threads and thread valleys are formed so that at least a part of the flank surface is composed of the porous body. A method for manufacturing a static pressure screw, comprising the steps of: forming the tubular base material from the outside to form a through hole reaching the porous body.