JP4216099B2 - Proportional valve, servo valve, proportional valve, or servo valve manufacturing method with hydrostatic bearing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a proportional valve and a servo valve having a hydrostatic bearing, and an improvement of a method for forming a surface restriction for a hydrostatic bearing on a sliding surface of a spool.
[0002]
[Prior art]
In every industry, miniaturization of processing and measurement control has rapidly progressed, and nanometer level positioning accuracy has been required in various fields.
[0003]
As such a field, for example, there is a semiconductor manufacturing technique, and it has become necessary to position a workpiece with high accuracy in a semiconductor exposure process or various processes related thereto.
[0004]
Conventionally, high-accuracy positioning is often performed by an electric linear motor. However, in a linear motor, generation of a magnetic field or heat becomes 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 an air servo valve or a pneumatic proportional valve, and it is possible to perform clean and non-viscous ultra-precision control.
[0005]
In such a proportional valve or servo valve, the spool is supported in the sleeve so as to be capable of linear movement in the axial direction, and a predetermined drive current is supplied to the movable wire wheel fixed to the spool, thereby allowing the linear movement position of the spool. Thus, a desired air pressure is supplied to the pneumatic actuator from the proportional valve or the servo valve. In order to smoothly move the spool in the sleeve and remove friction between the two as much as possible, it is preferable that the spool is hydrostatically supported.
[0006]
Normally, the static pressure bearing is provided on the sleeve on the fixed side, but 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]
JP-A-2002-297243
[Problems to be solved by the invention]
However, in the prior art as shown in Patent Document 1, compressed air is supplied from a compressed air supply source to an air blowing bearing provided in the spool via an air passage provided in the 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 static pressure bearing, and thereby the spool is supported in a non-contact manner with respect to the sleeve.
[0010]
Accordingly, such a conventional apparatus has a drawback that the apparatus is complicated, and is not suitable as a small ultra-precision proportional valve or servo valve for performing nanometer level control.
[0011]
In addition, a plurality of bearing portions for blowing air in the prior art are provided at intervals in the circumferential direction of the valve body so as not to overlap with the port. Such bearing portions are usually used as orifice (pocket) throttles. As is known, it consists of narrow holes drilled in the valve body, and such pores are often prone to clogging, and when used continuously, the pore diameter changes without going to clogging. As a result, the balance of the hydrostatic bearing support is easily lost, and there is a problem that the positioning control at the nanometer level is not reliable. The above-mentioned problem occurs in both the proportional valve and the servo valve, and the present invention aims to provide a proportional valve or a servo valve that solves such a conventional problem and enables super-precision positioning control. And
[0012]
[Means for Solving the Problems]
The proportional valve according to the present invention is pivotally supported in the sleeve so as to be axially linearly movable, and has a spool having a center land and both end lands arranged on both sides thereof, and is fixed to one end of the spool, and according to an input current. A movable wire ring that applies a straight driving force to the spool, a positioning spring that positions the spool at a predetermined axial position within the sleeve, and provides a reaction force against the driving force of the movable wire wheel to the spool, and a sleeve The gas supply pressure and exhaust pressure connected to the supply port and exhaust port are output to the load via the load port at a ratio corresponding to the relative position between the center land of the spool and the load port, and given to the movable wire ring. a proportional valve for outputting a gas pressure corresponding to the input current which is the load, one side of the gas chamber between the central land and two ends lands of the spool, the gas supply pressure of the supply port facing the supply port A gas chamber to be supplied remains, the other side is an exhaust chamber which is directly used as the exhaust pressure opposite the exhaust port, across the land of the spool, is used to generate an output gas pressure to the load supply A throttle for guiding the gas supply pressure of the port is provided as it is, and a static pressure bearing is formed between the sleeve and the throttle provided on the land facing the gas chamber among the lands on both ends, the gas supply pressure of the supply port remains unchanged. One end is open toward the gas chamber to be supplied, is formed along the axial direction of the land, and the other end is an elongated thin groove-shaped surface stop closed by the outer periphery of the land. The restriction provided on the land facing the chamber is formed along the axial direction of the land, with one end opening toward the introduction groove that communicates with the gas chamber and is supplied with the gas supply pressure of the supply port as it is. Is, other end, characterized in der Rukoto aperture elongated thin grooved surface to be closed by the outer periphery of the land.
[0014]
Further, the servo valve according to the present invention is axially supported in the sleeve so as to be axially movable, and has a spool having a center land and both end lands arranged on both sides thereof , fixed to one end of the spool, In response, a movable wire wheel that applies a straight driving force to the spool, a spool position detector that detects a spool position in the sleeve, and a gas supply pressure and an exhaust pressure connected to a supply port and an exhaust port provided in the sleeve. In the servo valve that outputs to the load through the load port at a rate according to the relative position between the center land of the spool and the load port, and outputs the gas pressure according to the input current given to the movable wire ring to the load, One side of the gas chamber between the center land and both ends lands of the spool is a gas chamber that faces the supply port and the gas supply pressure of the supply port is supplied as it is. Side is the exhaust chamber which is directly used as the exhaust pressure opposite the exhaust port, across the land of the spool, a diaphragm gas supply pressure of the supply port is introduced directly used to generate an output gas pressure to the load The throttle provided on the land facing the gas chamber among the lands on both ends is provided with a static pressure bearing between the sleeve and the one end toward the gas chamber to which the gas supply pressure of the supply port is supplied as it is. Opening and forming along the axial direction of the land, the other end is an elongated thin groove-like surface stop closed by the outer periphery of the land, and the stop provided on the land facing the exhaust chamber out of both ends land, One end opens toward the introduction groove that communicates with the gas chamber and is supplied with the gas supply pressure of the supply port as it is, and is formed along the axial direction of the land, and the other end is formed by the outer periphery of the land. Busy is the the elongated thin grooved surface aperture der wherein Rukoto.
[0015]
Further, in the proportional valve according to the present invention , a speed detector for detecting the straight speed of the spool is provided between the sleeve and the spool, and the damper is used for the straight movement of the spool by negatively feeding back the spool speed to the movable wire wheel. It is preferable to give an effect.
Further, in the proportional valve or the servo valve according to the present invention, the gas supply pressure is directly guided to the surface restriction provided on the supply pressure side land, and the surface restriction provided on the exhaust pressure side land is provided in the spool. It is preferable that the gas supply pressure is guided through the conduction path .
In the proportional valve or the servo valve according to the present invention, it is preferable that the surface restriction is composed of a plurality of thin grooves provided on the outer peripheral surface of the land along the linear movement direction of the spool.
Further, in the proportional valve or the servo valve according to the present invention, the surface throttle provided on the land opens toward the air chamber of the spool, and the outside of the spool may be blocked by the outer periphery of each land. preferable.
[0016]
Furthermore, in the method for manufacturing a proportional valve or servo valve according to the present invention , the surface of the bearing forming member is masked in the same shape as the surface restriction, and the entire surface of the bearing forming member is coated with a uniform plating layer. A surface restriction for a hydrostatic bearing is formed by including a process and a step of removing a masking from the bearing forming member and using the removed portion as a surface restriction.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a preferred first embodiment of a proportional valve having a hydrostatic bearing according to the present invention. In this embodiment, a three-way valve is formed, and a magnet case 12 and a case end 14 are firmly 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 compressed air source (not shown), the exhaust port EX is opened to the atmosphere, and the load port PL is connected to an air chamber of a pneumatic actuator (not shown).
[0018]
A spool 18 is pivotally supported in the sleeve 16 so as to be capable of linear movement in the axial direction. The spool 18 has three lands (valve bodies) 18a, 18b, 18c. When moving in the axial direction, the land 18b opens and closes the ports PS, EX, and PL, and the gas supply pressure and the exhaust pressure connected to the supply port PS and the exhaust port EX are proportional to the position of the spool 18. It can be 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 wound around and fixed to the coil bobbin 20. The aforementioned magnet case 12 is fixed with a ring-shaped permanent magnet 24 disposed opposite to the periphery of the movable wire ring 22, and the magnet case 12 itself is also made of a magnetic material. As a result, the movable wire ring 22 is made permanent. It will be placed in the magnetic field of the magnet 24. A predetermined input current is supplied from the terminal 26 to the movable wire ring 22, and as a result, the spool 18 can be linearly driven in the axial direction with a driving force corresponding to the input current.
[0020]
In order to localize the spool 18 in a predetermined axial position within the sleeve 16, localization springs 28 and 30 are disposed at both ends of the spool 18, and a reaction force that opposes the driving force of the movable wire ring 22 is spooled. 18 so that the spool 18 can move to a position corresponding to the input signal applied to the movable wire ring 22 and hold the position. When the position of the spool 18 is determined in this way, a predetermined gas pressure is output from the load port PL to the pneumatic actuator as a load, depending on the degree of opening of the ports PS and EX at this time. In order to adjust the no-load stationary position of the spool 18 by the positioning springs 28, 30, the axial position of one positioning spring 28 is adjusted by a zero point adjusting screw 32.
[0021]
What is characteristic in 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 the static pressure bearing comprises a surface aperture 34 provided on the outer peripheral surface of the land 18a. The surface diaphragm 34 is composed of a plurality of thin grooves provided on the outer peripheral surface of the land 18 a, and the thin grooves are formed along the linear movement direction of the spool 18. The surface diaphragm 34 formed of a 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 it out between the peripheral wall of the surface restrictor 34 and the sleeve 16, It becomes possible to obtain a desired non-contact hydrostatic 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 diaphragm 34 is closed by the outer periphery of the land 18a, and the left end of the land 18a is separated by a very small interval. It will be a hydrostatic bearing.
[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 a compressed air source for a special static pressure bearing as in the past is used. Can be a great advantage. 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]
On the land 18c side, a surface stop 40 similar to the surface stop 34 described above is formed. However, since the land 18c is adjacent to the exhaust port EX, it is used to guide the gas supply pressure from the supply port PS. Ingenuity has been made. That is, as shown in FIG. 1, the spool 18 is provided with a conduction hole 42. One end of the conduction hole 42 opens into the air chamber 36 communicating with the supply port PS, and the other end thereof is the land 18c. It opposes the introduction groove 44 provided in. In FIG. 3, this open end is shown as a plurality of openings 46 provided in the introduction groove 44. Accordingly, 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 in the land 18c. Thus, one end opening to the introduction groove 44 to the land 18c, by providing the other end along the surface aperture 40 is closed by the land 18c in the straight direction of the spool 18 into a plurality thin groove shape, shown in FIG. 2 described above As with the supply-side land 18a, a very stable static pressure bearing can be obtained.
[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 to the lands 18a and 18c on both sides of the spool 18, and the special static pressure bearing can be used. There is no need for a compressed air source and the like, the structure is simple, the apparatus is downsized, and it is possible to obtain an ultra-precision proportional valve of nanometer level.
[0027]
Further, the hydrostatic bearing according to the present invention can be composed of surface diaphragms 34 and 40 provided on the lands 18a and 18c. Unlike conventional orifice (pocket) diaphragms, such surface diaphragms 34 and 40 are thin grooves. Therefore, it is possible to provide an extremely stable hydrostatic bearing that is extremely resistant to clogging.
[0028]
FIG. 4 shows a servo valve according to a second embodiment of the present invention, which basically has a structure similar to 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 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 wheel 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 that is disposed facing the periphery of 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 in a part thereof. As a result, the detection coil 54 determines a detection signal determined by the position of the displacement shaft 52 from the terminal 56 depending on the position of the displacement shaft 52. Will be output. Therefore, by monitoring the output value of the terminal 56, the position of the spool 118 can be detected correctly, and a desired gas pressure can be supplied to the pneumatic actuator.
[0030]
Also in this servo valve, the spool 118 is provided with the surface restrictors 134 and 140 in the same manner as the proportional valve described above, and a static 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.
[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 improved version thereof, and the members corresponding to those in FIG. Detailed description is omitted.
[0033]
A characteristic feature 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 straight movement of the spool 218.
[0034]
Therefore, as apparent from FIG. 5, a coil bobbin 60 is also provided at the right end of the spool 218, and a search coil 62 is wound around the coil bobbin 60. A permanent magnet 64 is provided at the portion of the case end 214 that faces the search coil 62. As a result, the speed of the spool 218 becomes the electromotive force of the search coil 62 according to the axial movement of the spool 218, and the external from the terminal 66. Is output. The search coil 62 and the permanent magnet 64 constitute the speed detector of this 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 via a negative feedback loop (not shown), whereby a damper effect can be given to the straight movement of the spool 218.
[0036]
FIG. 6 shows the damper effect in the present embodiment, and the solid line exaggerates the position displacement when the spool 218 is driven, and an overshoot indicated by A can be seen, but as in this embodiment If the spool speed is negatively fed back, the overshoot can be reliably removed by the damper effect as indicated by the broken line characteristic B.
[0037]
Also in the third embodiment, the spool 218 is provided with a static pressure bearing, and the static pressure bearing obtains a pressure required for the bearing by the gas supply pressure from the supply port PS, and the static pressure bearing is configured by a simple structure. can do.
[0038]
Also in this embodiment, the diaphragm constituting the hydrostatic bearing is formed of a surface diaphragm, and can function as a bearing free from problems due to extremely stable clogging with a simple configuration.
[0039]
As described above, in the present invention, the surface diaphragm is formed on the land of the spool, but in order to obtain a static pressure bearing for performing ultra-precision position control at the nanometer level, its basic configuration The surface drawing must also be machined very precisely. Conventionally, such surface drawing has been formed by machining, etching or shot peening. However, there has been 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 precise processing cannot be performed. Therefore, in the present invention, masking is performed in advance on the portion to be the surface stop, and then the entire outer periphery of the land is plated to a predetermined thickness, and then the masking is removed to use the unplated recess as the surface stop. A surface drawing method is provided. Such surface drawing can be applied not only to the spool land in the above-described embodiment of the present invention but also to other flat surfaces or supports of any shape.
[0040]
FIG. 7 shows an example of the surface aperture forming method according to the present invention.
[0041]
FIG. 7A shows a bearing forming member 70 such as a land of a spool or a flat support, and a masking 72 is applied to a portion of the surface where a surface stop is to be formed. This masking can be obtained by sticking 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 process can be performed by a hard alumite process or a process corresponding thereto, or electroless nickel plating. In practice, since the plating is generally difficult to adhere to the masking 72, a plating layer is not formed on the surface thereof as shown in FIG. 7B. However, the masking 72 is reliably and accurately removed from the bearing forming member 70 in the next step. If they can be separated, the surface drawing method according to the present invention can be realized even if the plating layer 74 is deposited on the masking 72.
[0043]
In addition, prior to the main plating, a similar or different plating method may be used to improve plating adhesion and to mask the masked portion in advance.
[0044]
The thickness of the plating layer 74 determines the depth of the surface drawing in the present invention, and is selected in the range of 10 to 20 μm in the embodiment.
[0045]
Next, as shown in FIG. 7C, the masking 72 is removed from the bearing forming member 70, whereby the surface diaphragm 76 can be obtained in the portion where the masking 72 has been removed.
[0046]
As described above, according to the surface aperture forming method of the present invention, it is possible to easily obtain a surface aperture even with a very simple and complicated shape, and particularly when performing ultrafine static control. Very suitable for obtaining pressure bearings.
[0047]
【The invention's effect】
As described above, according to the present invention, a static pressure bearing can be configured very easily in a proportional valve or servo valve, and a proportional valve or servo valve useful for ultraprecision control can be obtained.
[0048]
Further, it is possible to form such a surface diaphragm for a static pressure bearing by a simple method.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a main part of a proportional valve according to a first embodiment of the present invention.
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 an exhaust port side static pressure bearing of the embodiment shown in FIG. 1; FIG.
FIG. 4 is a cross-sectional view of a main part showing a servo valve according to a second embodiment of the present invention.
FIG. 5 is a cross-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 surface aperture forming method 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 element), 22, 122, 222 Movable Wire ring, 28, 30, 228, 230 Localized spring, 34 , 40 , 134, 140, 234 , 240 Surface restriction, 52, 54 Spool position detector, 62, 64 Speed detector, PS supply port, EX exhaust port , PL load port.

Claims (7)

A spool that is pivotally supported in the sleeve so as to be axially linearly movable and has a center land and both end lands disposed on both sides thereof ;
A movable wire ring that is fixed to one end of the spool and applies a straight driving force to the spool in response to an input current;
A localization spring that positions the spool in a predetermined axial position within the sleeve and applies a reaction force against the driving force of the movable wire wheel to the spool;
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 through the load port at a ratio according to the relative position between the center land of the spool and the load port , In the proportional valve that outputs the gas pressure corresponding to the input current given to the movable wire ring to the load,
One side of the gas chamber between the center land and both ends lands of the spool is a gas chamber that faces the supply port and the gas supply pressure of the supply port is supplied as it is, and the other side faces the exhaust port and the exhaust pressure is left as it is. Is an exhaust chamber,
A static pressure bearing is formed between the lands on both ends of the spool by providing a throttle to guide the gas supply pressure of the supply port used for generating the output gas pressure to the load as it is,
The diaphragm provided in the land facing the gas chamber among the lands on both ends is formed along the axial direction of the land with one end opening toward the gas chamber to which the gas supply pressure of the supply port is supplied as it is, It is an elongated thin groove-shaped surface stop whose end is closed by the outer periphery of the land,
Of the lands on both ends, the throttle provided on the land facing the exhaust chamber opens at one end toward the introduction groove that communicates with the gas chamber and is supplied with the gas supply pressure of the supply port as it is. along formed and the other end proportional valve, characterized in der Rukoto aperture elongated thin grooved surface to be closed by the outer periphery of the land. A spool that is pivotally supported in the sleeve so as to be axially linearly movable and has a center land and both end lands disposed on both sides thereof ;
A movable wire ring that is fixed to one end of the spool and applies a straight driving force to the spool in response 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 through the load port at a ratio according to the relative position between the center land of the spool and the load port , In the servo valve that outputs the gas pressure corresponding to the input current given to the movable wire ring to the load,
One side of the gas chamber between the center land and both ends lands of the spool is a gas chamber that faces the supply port and the gas supply pressure of the supply port is supplied as it is, and the other side faces the exhaust port and the exhaust pressure is left as it is. Is an exhaust chamber,
A static pressure bearing is formed between the lands on both ends of the spool by providing a throttle to guide the gas supply pressure of the supply port used for generating the output gas pressure to the load as it is,
The diaphragm provided in the land facing the gas chamber among the lands on both ends is formed along the axial direction of the land with one end opening toward the gas chamber to which the gas supply pressure of the supply port is supplied as it is, It is an elongated thin groove-shaped surface stop whose end is closed by the outer periphery of the land,
Of the lands on both ends, the throttle provided on the land facing the exhaust chamber opens at one end toward the introduction groove that communicates with the gas chamber and is supplied with the gas supply pressure of the supply port as it is. along formed, servovalve other end, characterized in elongated thin grooved surface aperture der Rukoto which is closed by the outer periphery of the land. The proportional valve according to claim 1,
A speed detector is provided between the sleeve and the spool to detect the straight speed of the spool.
A proportional valve characterized by giving a damper effect to the straight movement of the spool by negatively feeding back the spool speed to the movable wheel . The proportional valve or servo valve according to any one of claims 1 to 3 ,
The gas supply pressure is directly guided to the surface restriction 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 in an exhaust pressure side land through a conduction path provided in a spool . In the proportional valve or the servo valve according to any one of claims 1 to 4 ,
The proportional restriction valve or servo valve is characterized in that the surface restriction is composed of a plurality of thin grooves provided on the outer peripheral surface of the land along the linear movement direction of the spool . In the proportional valve or servo valve according to any one of claims 1 to 5 ,
The surface diaphragm provided in the land opens toward the air chamber of the spool,
A proportional valve or servo valve characterized in that the outside of the spool is closed by the outer periphery of each land . A method for manufacturing a proportional valve or a servo valve according to any one of claims 1 to 6 ,
A step of masking the surface of the bearing forming member in the same shape as the surface diaphragm;
A process of depositing the entire surface of the bearing forming member with a uniform plating layer;
Removing the masking from the bearing forming member and setting the removed portion as a surface aperture;
A method for manufacturing a proportional valve or a servo valve , comprising forming a surface restriction for a hydrostatic bearing .

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