JP2004270870A - Proportional valve and servo valve with static pressure bearing, and method of forming surface- drawing for static pressure bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a proportional valve and a servo valve with a static pressure bearing mechanism which can perform highly precise position control, and a method of forming a static pressure bearing. <P>SOLUTION: The static pressure bearings are provided on lands 18a, 18c of a spool 18 which is movable within a sleeve 16. The static pressure bearings include surface-drawing 34, 40 formed on the outer peripheral surfaces of the respective lands 18a, 18c. Gas supply pressure is introduced from a supply port PS to the surface-drawing 34, 40. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a proportional valve and a servo valve having a hydrostatic bearing, and to an improvement in a method of forming a surface throttle for a hydrostatic bearing on a sliding surface of a spool.
[0002]
[Prior art]
In all industries, processing and measurement control have been miniaturized rapidly, and positioning accuracy on the order of nanometers has been required in various fields.
[0003]
In such a field, for example, there is a semiconductor manufacturing technique. In a semiconductor exposure process or various processes related thereto, it has been necessary to position a workpiece with high accuracy.
[0004]
Conventionally, high-precision positioning has been often performed by an electric linear motor.However, in a linear motor, generation of a magnetic field or heat has become a problem, and a pneumatic actuator has been used as an alternative positioning drive control actuator. . Normally, a pneumatic actuator is supplied with a desired gas pressure by a pneumatic servo valve or a pneumatic proportional valve, thereby enabling clean and viscous ultra-precision control.
[0005]
In such a proportional valve or servo valve, a spool is supported in a sleeve so as to be able to move directly in the axial direction, and a predetermined drive current is supplied to a movable wire fixed to the spool, so that the spool can move directly. , Whereby a desired air pressure is supplied to the pneumatic actuator from a proportional valve or a servo valve. It is preferable that the spool be subjected to a static pressure bearing in order to smoothly move the spool in the sleeve and to remove friction between the two as much as possible.
[0006]
Normally, the static pressure bearing is provided on the sleeve on the fixed side. However, as shown in Patent Document 1, a structure in which a static pressure bearing is provided on the spool side is also known.
[0007]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2002-297243
[Problems to be solved by the invention]
However, in the related art as disclosed in Patent Document 1, compressed air is supplied from a compressed air supply source to an air blowing bearing provided on a spool through an air passage provided on a shaft of the spool. There was a problem that had to be.
[0009]
That is, in such a conventional apparatus, a special compressed air source is provided for the hydrostatic bearing, and thereby the spool is supported in a non-contact manner with respect to the sleeve.
[0010]
Therefore, such a conventional apparatus has a drawback that the apparatus becomes complicated and is not particularly suitable as a small ultra-precision proportional valve or a servo valve for controlling at the nanometer level.
[0011]
In the prior art, a plurality of bearings for air blowing are provided at intervals in the circumferential direction of the valve body so as not to overlap with the port. Such bearings are usually provided as orifice (pocket) throttles. As is known, it is composed of small holes drilled in the valve body, such pores are often easily clogged, and when used continuously, the hole diameter changes even if it does not go to clogging. Therefore, there is a problem that the balance of the support of the hydrostatic bearing is easily lost, and the reliability of the positioning control at the nanometer level is poor. The above-mentioned problem similarly occurs in the proportional valve and the servo valve. The present invention has been made to solve the conventional problem and to provide a proportional valve or a servo valve capable of performing ultra-precise positioning control. And
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a spool that is axially supported in a sleeve so as to be capable of linearly moving in an axial direction, and a movable wire loop that is fixed to one end of the spool and applies a linear driving force to the spool in accordance with an input current. And a positioning spring for positioning the spool at a predetermined axial position within the sleeve and applying a reaction force against the driving force of the movable wire to the spool, and a gas connected to a supply port and an exhaust port provided on the sleeve. In a proportional valve that outputs the supply pressure and the exhaust pressure to the load at a ratio according to the position of the spool, and outputs the gas pressure according to the input current given to the movable wire to the load, the gas supply pressure is applied to the spool land. A throttle is provided to form a static pressure bearing between the sleeve and the sleeve, and a gas supply pressure from a supply port is guided to the throttle.
[0013]
The present invention also provides a spool which is axially supported in a sleeve so as to be capable of linearly moving in an axial direction, a movable wire loop which is fixed to one end of the spool and applies a linear driving force to the spool in accordance with an input current, and And a localizing spring that applies a reaction force against the driving force of the movable wire loop to the spool, a gas supply pressure and an exhaust pressure connected to a supply port and an exhaust port provided in the sleeve. Output to the load at a rate according to the position of the spool, and outputs a gas pressure according to the input current applied to the movable wire to the load. And a static pressure bearing is formed between the first and second lands, and the iris comprises a surface iris formed on the outer peripheral surface of the land.
[0014]
Further, the present invention provides a spool which is axially supported in the sleeve so as to be capable of linearly moving in the axial direction, a movable wire loop fixed to one end of the spool and which applies a linear driving force to the spool in accordance with an input current, and a spool in the sleeve. A spool position detector for detecting the position, and a gas supply pressure and an exhaust pressure connected to a supply port and an exhaust port provided on the sleeve are output to a load at a ratio according to the position of the spool, and applied to a movable wire ring. In a servo valve that outputs a gas pressure corresponding to an input current to a load, a restrictor that guides a gas supply pressure is provided on a land of a spool to form a static pressure bearing between the spool and a sleeve. A gas supply pressure is introduced.
[0015]
Further, the present invention provides a spool which is axially supported in a sleeve so as to be capable of linearly moving in an axial direction, a movable wire loop which is fixed to one end of the spool and applies a linear driving force to the spool in accordance with an input current, and a spool in a sleep. A spool position detector for detecting the position, and a gas supply pressure and an exhaust pressure connected to a supply port and an exhaust port provided on the sleeve are output to a load at a ratio according to the position of the spool, and applied to a movable wire ring. In a servo valve that outputs a gas pressure corresponding to an input current to a load, a throttle that guides a gas supply pressure is provided on a land of a spool to form a static pressure bearing between the spool and a sleeve, and the throttle is formed on an outer peripheral surface of the land. It is characterized by comprising a formed surface drawing.
[0016]
Further, the present invention provides a step of masking the surface of the bearing forming member with the same shape as the surface drawing, a step of applying the entire surface of the bearing forming member with a uniform plating layer, and removing the masking from the bearing forming member. And removing the removed portion to form a surface drawing.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a first preferred embodiment of a proportional valve having a hydrostatic bearing according to the present invention. This embodiment comprises a three-way valve, and a magnet case 12 and a case end 14 are firmly and closely fixed to both ends of a cylindrical housing 10. A sleeve 16 is fixed inside the housing 10, and the housing 10 and the sleeve 16 are provided with a supply port PS, an exhaust port EX, and a load port PL for forming a three-way valve. The supply port PS is connected to a source of compressed air (not shown), the exhaust port EX is open to the atmosphere, and the load port PL is connected to the air chamber of a pneumatic actuator not shown.
[0018]
A spool 18 is axially supported in the sleeve 16 so as to be able to linearly move in the axial direction. The spool 18 has three lands (valve elements) 18a, 18b, and 18c. When moving in the axial direction, the land 18b opens and closes each of the ports PS, EX, and PL, and adjusts the gas supply pressure and the exhaust pressure connected to the supply port PS and the exhaust port EX at a ratio according to the position of the spool 18. It can output to the load port PL.
[0019]
A coil bobbin 20 is formed at one end of the spool 18, and a movable wire ring 22 is fixedly wound around the coil bobbin 20. A ring-shaped permanent magnet 24 is fixed to the above-described magnet case 12 so as to be opposed to the periphery of the movable wire ring 22, and the magnet case 12 itself is also made of a magnetic material. It will be located in the magnetic field of the magnet 24. A predetermined input current is supplied to the movable wire ring 22 from the terminal 26. As a result, the spool 18 can be driven straight in the axial direction with a driving force corresponding to the input current.
[0020]
Positioning springs 28 and 30 are disposed at both ends of the spool 18 to localize the spool 18 at a predetermined axial position in the sleeve 16, and the reaction force against the driving force of the movable wire 22 is applied to the spool 18. 18, whereby the spool 18 can be moved to a position corresponding to the input signal given to the movable wire ring 22 and hold that position. When the position of the spool 18 is determined in this manner, a predetermined gas pressure is output from the load port PL to the pneumatic actuator as a load depending on the opening state of each port PS and EX at this time. In order to adjust the no-load rest position of the spool 18 by the localization springs 28 and 30, the axial position of one of the localization springs 28 is adjusted by a zero-point adjusting screw 32.
[0021]
A feature of the present invention is that the proportional valve has a hydrostatic bearing. In the present invention, the hydrostatic bearing is provided on the spool 18.
[0022]
FIG. 2 shows a static pressure bearing provided on the land 18a of the spool 18, and this static pressure bearing comprises a surface stop 34 provided on the outer peripheral surface of the land 18a. The surface stop 34 is composed of a plurality of thin grooves provided on the outer peripheral surface of the land 18a, and these thin grooves are formed along the direction of the linear movement of the spool 18. The surface throttle 34 formed of the thin groove opens toward the air chamber 36 of the spool 18 and is closed by the outer periphery of the land 18a with respect to the exhaust chamber 38 outside the spool. That is, the right end of the surface restrictor 34 opens toward the air chamber 36, guides the gas pressure from the supply port PS supplied to the air chamber 36, and blows out the gas pressure from the peripheral wall of the surface restrictor 34 to the sleeve 16. It is possible to obtain a desired non-contact static pressure bearing action. In order to obtain a desired static pressure between the land 18a and the sleeve 16, as described above, the left end of the surface stop 34 is closed by the outer periphery of the land 18a, and the left end of the land 18a is formed with a very small interval. Between the bearings.
[0023]
As described above, according to the present invention, the gas supply pressure from the supply port PS is directly guided to the throttle 34 for forming the static pressure bearing, and the compressed air source for the special static pressure bearing is used as in the related art. The great advantage that it is not required can be shown. The gas in the exhaust chamber 38 described above is exhausted to the outside through an exhaust hole 10 a provided in the housing 10.
[0024]
Next, the land 18c of the spool 18 on which the other hydrostatic bearing is formed will be described in detail with reference to FIG.
[0025]
A surface stop 40 similar to the above-described surface stop 34 is also formed on the land 18c side. However, since the land 18c is adjacent to the exhaust port EX, the land 18c is used to guide the gas supply pressure from the supply port PS. Something has been devised. That is, as shown in FIG. 1, the spool 18 is provided with a conduction hole 42, one end of which is open to the air chamber 36 communicating with the supply port PS, and the other end of which has the land 18c. Is opposed to the introduction groove 44 provided at the bottom. In FIG. 3, the opening ends are shown as a plurality of openings 46 provided in the introduction groove 44. Therefore, the gas supply pressure connected to the supply port PS is guided to the introduction groove 44, and the air chamber 48 communicating with the exhaust port EX is shielded by the ring wall 50 provided on the land 18c. Therefore, if one end of the land 18c is opened in the introduction groove 44 and the multiple ends are closed by the land 18c and the surface stop 40 is provided in a plurality of thin grooves along the straight traveling direction of the spool 18, it is shown in FIG. An extremely stable hydrostatic bearing can be obtained as in the case of the land 18a on the supply side.
[0026]
Therefore, according to the present invention, the gas supply pressure of the supply port PS can be used as it is as the gas supply pressure for the static pressure bearing on the lands 18a and 18c on both sides of the spool 18, and the special static pressure bearing can be used. This eliminates the need for a compressed air source or the like, makes the structure simple, makes the device compact, and makes it possible to obtain an extremely super-precision proportional valve on the nanometer level.
[0027]
Further, the hydrostatic bearing according to the present invention can be constituted by surface restrictors 34, 40 provided on the lands 18a, 18c. Unlike the conventional orifice (pocket) restrictors, such surface restrictors 34, 40 have thin grooves. , Which has a wide and shallow peripheral wall, is extremely resistant to clogging, and can provide an extremely stable hydrostatic bearing.
[0028]
FIG. 4 shows a servo valve according to a second embodiment of the present invention, which basically has a structure similar to that of the proportional valve shown in FIG. 1 as a servo valve for controlling a pneumatic actuator. Therefore, the corresponding members are indicated by adding 100 to the reference numerals, and the detailed description is omitted.
[0029]
In the servo valve shown in FIG. 4, the linear movement position of the spool 118 is always detected, and the drive current supplied to the movable wire 122 is controlled in accordance with this position. For this purpose, the spool 18 is provided with a displacement shaft 52 made of a magnetic material, while the housing 110 is provided with a detection coil 54 disposed around and around the displacement shaft 52. These displacement shaft 52 and detection coil 54 form a spool position detector. The displacement shaft 52 itself is made of a magnetic material or a magnetic material is fitted into a part thereof. As a result, depending on the position of the displacement shaft 52, the detection coil 54 outputs a detection signal determined by the position of the displacement shaft 52 from the terminal 56. Will be output. Therefore, by monitoring the output value of the terminal 56, the position of the spool 118 can be correctly detected, and a desired gas pressure can be supplied to the pneumatic actuator.
[0030]
Also in this servo valve, the spools 118 are provided with surface throttles 134 and 140 similarly to the above-described proportional valve, and a static body bearing can be obtained by the gas supply pressure of the supply port PS.
[0031]
The structure of the diaphragm in this embodiment is the same as that of the embodiment shown in FIGS. 1 to 3, and a detailed description is omitted.
[0032]
FIG. 5 shows a third embodiment of the present invention, which is similar to the proportional valve shown in FIG. 1 but is an improvement thereof, and the members corresponding to those of FIG. The detailed description is omitted.
[0033]
A characteristic of the third embodiment is that the moving speed of the spool 218 is measured, and the spool speed is negatively fed back to the movable wire ring 222 to give a damper effect to the linear movement of the spool 218.
[0034]
To this end, a coil bobbin 60 is also provided at the right end of the spool 218, and a search coil 62 is fixedly wound around the coil bobbin 60, as is apparent from FIG. A permanent magnet 64 is provided at a portion of the case end 214 facing the search coil 62. As a result, the speed becomes the electromotive force of the search coil 62 according to the axial movement of the spool 218, and the terminal 66 Output to The search coil 62 and the permanent magnet 64 constitute a speed detector of the present embodiment.
[0035]
The spool speed, which is the output of the terminal 66, is supplied to the drive circuit of the movable wire ring 222 through a negative feedback loop (not shown), whereby the linear movement of the spool 218 can be given a damper effect.
[0036]
FIG. 6 shows the damper effect in the present embodiment. The solid line exaggerates the position displacement when the spool 218 is driven, and an overshoot indicated by A is seen. If the spool speed is negatively fed back, the overshoot can be reliably removed by the damper effect as shown by the characteristic B in the broken line.
[0037]
Also in the third embodiment, a static pressure bearing is provided on the spool 218, and the static pressure bearing obtains the pressure required for the bearing by the gas supply pressure from the supply port PS, and constitutes the static pressure bearing with a simple structure. can do.
[0038]
Also in this embodiment, the throttle constituting the hydrostatic bearing is formed from a surface throttle, and can function as a bearing having a simple configuration and having no problem due to extremely stable clogging.
[0039]
As described above, in the present invention, the surface iris is formed on the land of the spool, but in order to obtain a hydrostatic bearing for performing ultra-precision position control on the nanometer level, the basic configuration thereof is required. Must also be processed very precisely. Conventionally, such a surface drawing is formed by machining, etching or shot peening. However, there is a problem that it is difficult to perform these forming processes on a curved surface such as a land of a spool as in the present invention, and that precise processing cannot be performed. Therefore, in the present invention, masking is performed in advance on a portion to be a surface drawing, then the entire outer periphery of the land is plated to a predetermined thickness, and then the masking is removed, so that the unplated concave portion is used as the surface drawing. A method for forming a surface drawing is provided. Such surface drawing can be applied not only to the land of the spool in the above-described embodiment of the present invention but also to a support having another flat surface or an arbitrary shape.
[0040]
FIG. 7 shows an example of the surface drawing forming method according to the present invention.
[0041]
FIG. 7A shows a bearing forming member 70 such as a spool land or a flat support. A masking 72 is applied to a portion of the surface where a surface drawing is to be formed. This masking is obtained by sticking using a tape or the like as a mask, applying a solvent in a desired shape, or masking with a jig.
[0042]
Next, as shown in FIG. 7B, a plating layer 74 is formed on the entire surface of the bearing forming member 70. This plating treatment can be performed by a hard alumite treatment or a treatment equivalent thereto, or electroless nickel plating. Actually, since the plating is generally not easily adhered to the masking 72, a plating layer is not formed on the surface thereof as shown in FIG. 7B. However, the masking 72 can be reliably and accurately removed from the bearing forming member 70 in the next step. If it can be separated, the method for forming a surface drawing according to the present invention can be realized even if the plating layer 74 is applied on the masking 72.
[0043]
Further, prior to the main plating, a similar or different plating may be performed in advance in order to improve the adhesion of the plating and to perform plating on the masked portion.
[0044]
The thickness of the plating layer 74 determines the depth of the surface drawing in the present invention, and is selected in the embodiment from 10 to 20 micrometers.
[0045]
Next, as shown in FIG. 7C, the masking 72 is removed from the bearing forming member 70, whereby a surface stop 76 can be obtained in the portion where the masking 72 has been removed.
[0046]
As described above, according to the surface drawing forming method of the present invention, it is possible to easily obtain a surface drawing even in an extremely simple and complicated shape, and in particular, to perform ultra-precision static control when controlling at the nanometer level. Very suitable for obtaining pressure bearings.
[0047]
【The invention's effect】
As described above, according to the present invention, in a proportional valve or a servo valve, a static pressure bearing can be configured very easily, and a proportional valve or a servo valve useful for ultra-precision control can be obtained.
[0048]
In addition, it is possible to form such a surface aperture for a hydrostatic bearing by a simple method.
[Brief description of the drawings]
FIG. 1 is a sectional view of a main part showing a proportional valve according to a first embodiment of the present invention.
FIG. 2 is a perspective view showing a main part of a supply port side static pressure bearing of the proportional valve shown in FIG. 1;
FIG. 3 is a perspective view showing a main part of the exhaust port side static pressure bearing of the embodiment shown in FIG. 1;
FIG. 4 is a sectional view showing a main part of a servo valve according to a second embodiment of the present invention.
FIG. 5 is a sectional view showing a main part of a proportional valve according to a third embodiment of the present invention.
FIG. 6 is an explanatory diagram showing the operation of the third embodiment.
FIG. 7 is an explanatory view showing a method for forming a surface drawing according to the present invention.
[Explanation of symbols]
10, 110, 210 Housing, 16, 116, 216 Sleeve, 18, 118, 218 Spool, 18a, 18b, 18c, 118a, 118b, 118c, 218a, 218b, 218c Land (valve), 22, 122, 222 Movable Wire loop, 28, 30, 228, 230 Oriented spring, 34, 40, 134, 140, 234, 240 Surface throttle, 52, 54 Spool position detector, 62, 64 Speed detector, PS supply port, EX exhaust port , PL load port.

Claims (9)

A spool axially supported in the sleeve so as to be able to move directly in the axial direction,
A movable wire loop fixed to one end of the spool and applying a linear driving force to the spool according to an input current;
A positioning spring that positions the spool at a predetermined axial position within the sleeve and applies a reaction force to the spool that opposes the driving force of the movable wire loop;
The gas supply pressure and the exhaust pressure connected to the supply port and the exhaust port provided in the sleeve are output to the load at a ratio according to the position of the spool, and the gas pressure according to the input current applied to the movable wire is loaded. Output to the proportional valve,
A restrictor for guiding gas supply pressure is provided on the land of the spool to form a static pressure bearing between the sleeve and the sleeve,
A proportional valve, wherein a gas supply pressure from a supply port is led to the throttle. A spool axially supported in the sleeve so as to be able to move directly in the axial direction,
A movable wire loop fixed to one end of the spool and applying a linear driving force to the spool according to an input current;
A positioning spring that positions the spool at a predetermined axial position within the sleeve and applies a reaction force to the spool that opposes the driving force of the movable wire loop;
The gas supply pressure and the exhaust pressure connected to the supply port and the exhaust port provided in the sleeve are output to the load at a ratio according to the position of the spool, and the gas pressure according to the input current applied to the movable wire is loaded. Output to the proportional valve,
A restrictor for guiding gas supply pressure is provided on the land of the spool to form a static pressure bearing between the sleeve and the sleeve,
The proportional valve according to claim 1, wherein the throttle comprises a surface throttle formed on an outer peripheral surface of the land. A spool axially supported in the sleeve so as to be able to move directly in the axial direction,
A movable wire loop fixed to one end of the spool and applying a linear driving force to the spool according to an input current;
A spool position detector for detecting a spool position in the sleeve,
The gas supply pressure and the exhaust pressure connected to the supply port and the exhaust port provided in the sleeve are output to the load at a ratio according to the position of the spool, and the gas pressure according to the input current applied to the movable wire is loaded. In the servo valve that outputs to
A restrictor for guiding gas supply pressure is provided on the land of the spool to form a static pressure bearing between the sleeve and the sleeve,
A servo valve, wherein a gas supply pressure from a supply port is led to the throttle. A spool axially supported in the sleeve so as to be able to move directly in the axial direction,
A movable wire loop fixed to one end of the spool and applying a linear driving force to the spool according to an input current;
A spool position detector for detecting a spool position in sleep;
The gas supply pressure and the exhaust pressure connected to the supply port and the exhaust port provided in the sleeve are output to the load at a ratio according to the position of the spool, and the gas pressure according to the input current applied to the movable wire is loaded. In the servo valve that outputs to
A restrictor for guiding gas supply pressure is provided on the land of the spool to form a static pressure bearing between the sleeve and the sleeve,
A servo valve according to claim 1, wherein said throttle comprises a surface throttle formed on an outer peripheral surface of a land. The proportional valve according to claim 1 or 2,
A speed detector that detects the straight traveling speed of the spool is provided between the sleeve and the spool,
A proportional valve characterized by giving a damper effect to the linear movement of the spool by negatively returning the spool speed to the movable wire. In the proportional valve or the servo valve according to any one of claims 2 or 4,
The gas supply pressure is directly led to the surface throttle provided on the supply pressure side land,
A proportional valve or a servo valve, wherein a gas supply pressure is guided to a surface throttle provided on an exhaust pressure side land via a conduction path provided in a spool. The proportional valve or the servo valve according to any one of claims 2, 4, and 6,
The proportional valve or the servo valve, wherein the surface throttle is formed of a plurality of thin grooves provided on the outer peripheral surface of the land along the direction of linear movement of the spool. The proportional valve or the servo valve according to any one of claims 2, 4, 6, and 7,
The surface stop provided on the land opens toward the air chamber of the spool,
A proportional valve or a servo valve, wherein the outside of the spool is closed by the outer periphery of each land. A step of masking the surface of the bearing forming member in the same shape as the surface drawing,
A step of applying the entire surface of the bearing forming member with a uniform plating layer,
A method of forming a surface drawing for a hydrostatic bearing, comprising a step of removing the masking from the bearing forming member and making the removed portion a surface drawing.

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